Como eu construo o tanque / curandeiro Paladin que meu grupo precisa sem ter várias classes no Pathfinder?

Paladin as a tank / healer in combat is possible, but inefficient.

Building a Pathfinder character is all about tradeoffs. By mixing roles of frontliner and healing support, you can't really specialize at both effectively; you output less damage than a dedicated attacker, and restore less HP than a dedicated healer. Support casters often struggle in the front lines, because they're either busy attacking (i.e., not healing) or are taking too many hits.

Paladino is an ok choice, although their healing and support role is secondary to their melee power. Paladins are suited as a tank in combat, and a support/healer out of combat. However, they can still manage the combat medic role if planned and played strategically, and it sounds like you're set on pure paladin.

Usually, healing is best performed out of combat. Early on, a wand of Curar feridas leves will be helpful. Eventually you'll want wands of higher-level paladin spells como Restauração menor.

A paladin's healing/support capacity improves at medium levels (5-10, usually). Combat healing in Pathfinder is suboptimal, because HP is typically lost faster than it can be regained. Therefore it's better to prevent incoming damage, by engaging and defeating enemies, than to spend your turns as a band-aid. There are exceptions (e.g. Curar) but paladins don't reach that level of spellcasting.

Combat tactics:

• Buff and heal sparingly, as needed. Your spells per day are very limited. Outside of melee, you should rely on wands and scrolls.

• Don't wait for the enemies to rush your party. Move into tank position as soon as possible. If you expect a difficult fight, maybe cast a buff spell for yourself and/or allies on round 1.

• Prioritize tanking over healing. When you're in melee and a nearby ally is getting low on health, the enemy is your immediate threat. Deal with the enemy first, then assist your allies.

• Encourage your allies to carry healing items (e.g. potions). If your allies can heal themselves via their own action economy, then you can spend your turns more effectively.

Useful feats:

• Ataque Poderoso. Useful for many tanks, especially with 2-handed weapons. Select your tank and frontliner feats early, since you can't cast at low levels anyway.

• Reward of Life. Make your Lay on Hands more effective, because Paladins have more daily uses of Lay on Hands than spell slots for healing spells.

• Fundição de Combate. Although 5-foot stepping away from your opponent is often the easiest way to cast spells, sometimes it's not enough (e.g., your enemy has natural reach) and you'll need to cast defensively. Concentration checks are tough for a Paladin because their caster level lags behind the primary casters, and so a +4 bonus will help.

• Canalização seletiva. Tanky characters tend to be near enemies. This feat lets you channel positive energy to heal your allies without helping your opponents.

Archetypes:

I recommend none. Many of the paladin archetypes replace one or more of your Aura class features, which is a mediocre tradeoff. Because your Aura abilities are passive effects, exchanging one for a standard action ability hurts your action economy. Also, since you're going to level 20, your party will need reliable saving throws versus the onslaught of save-or-die effects; they benefit more from the Aura's bonuses.

Healing HP Between Combats—Use a Wand

Compre um varinha de curar feridas leves, and use it between battles. You can use this right from 1st level, even before you have spellcasting of your own, without any checks, and a party of four can generally pool wealth together to buy one before even hitting 2nd level.

This will literally handle all the HP-healing the party should need. Frankly, there is no better healing in the game besides the curar spell, which you cannot get as a paladin, so if your party needs more healing than that, then they are just out of luck; Pathfinder just doesn’t offer enough tools to help them. In combat, your job is to just focus on killing threats before they can kill your allies.

Healing Status Conditions Between Combats—Mercies or restauração

Later, when you can, prepare restauração menor or restauração as needed. Having a rolagem of these spells may work better; a varinha may be overkill/too expensive. Your paladin mercies will cover some of the conditions that these kinds of spells heal, as well, which makes it less critical to prepare these spells regularly.

Actually, this is one of the very, very few cases where a potion can make sense: a potion of lesser restoration can be drank more swiftly than the spell itself can be cast, and it can be used by all members of the party. Potions are overpriced, but if everyone holds on to just one for a rainy day, that could salvage a very dicey situation.

Healing More Serious Status Conditions—Find a Cleric

Keep in good graces with your church, so you can run to a temple and get a cleric to bust out the bigger condition-healing spells than you can currently cast, like quebrar o encantamento before you have 4th-level paladin spells. You could conceivably have a staff to cover these problems, but it would be fantastically expensive (which would definitely cut into your ability to deal or take damage).

Healing in Combat—Do Not Except in the Most Extreme Emergencies

Get your enemies dead first. Combat goes too fast, and your healing is too slow, to attempt to actually bring anyone back to combat-ready in the middle of a fight. Only the curar spell can do that. The only time healing should occur during combat is in an absolute emergency, when that healing is the line between life and death. With how little you can heal, that will be very rare.

The vast majority of combats in Pathfinder are decided in the first two or three rounds. They may linger somewhat longer than that, but by then the fight has almost-always been decided. Giving up a third to a half of your combat presence to partially-undo a single attack against an ally is just a waste of time, and that’s what the numbers work out to. This is always a mistake unless it saves someone’s life.

Improving your Healing—Don’t, You Need Those Resources

This is the harsh reality of this system: paladins are among the weakest classes in the game, combat healing is among the weakest potential tactics one can turn to, and the paladin is not in any way well-suited to trying to do it. Focus on doing what the class can actually try to do—get the enemy dead—and you may actually succeed. But it’s going to take everything you can get to make you good enough at that. You have nothing to spare trying—and failing—to get better at healing.

Your out-of-combat healing is good enough. Your in-combat healing can Nunca be good enough. Therefore, you should not invest any scarce resources into healing more than this. That means no feats, no items, no archetypes devoted to healing. They are, all of them, bad, traps you should not take nor should anyone else.

In particular, definitely do not take the hospitaler archetype. It’s a trap; channel energy is weak and it’s even weaker for a hospitaler than it is for a cleric. The aura of healing is absurdly weak for 11th level.

Se vocês estão going to sacrifice your damage output for protecting your allies, the sacred shield archetype is vastly superior, and will actually reduce the damage your allies take by a fair margin (it will also reduce the damage you deal by quite a lot, however, since bastion of good replaces smite evil). But realistically, again, the best approach to keeping your party alive, as far as archetypes are concerned, is to kill your enemies as fast as possible. Your archetype should support that. The sacred shield option would be much better for an oradin than a paladin, since an oradin would have quality spellcasting to replace their smite-boosted attacks.

About Tanking—Pathfinder Has No Such Thing

A note on “tanking”—there is almost-zero ability in Pathfinder to do it properly. You can defend yourself, but you cannot easily offer any active defense for allies. The proteger outro spell is available to you, you could get Reflexos de combate e Viagem melhorada and a reach weapon if you wanted, but these things are small and all-too-easily ignored. And if you focus too much on your own defenses, enemies can and should just ignore you and go after your allies, who are simultaneously easier to kill and far more dangerous to leave alive. In order to get enemies’ attention on you (and thus away from your allies), you need to be either scary or annoying enough to demand that attention. Again, for a paladin, that mostly means dealing enough damage that you cannot be ignored.

Ironically, one of the most effective ways to deal damage as a paladin is as an archer. This also makes you somewhat less obviously-tough-to-kill, which may actually work in your favor as your enemies think they can deal with the dangerous archer quickly, and then you turn out to be tougher than expected. However, this seems quite likely to not be what you are looking for, and kind of goes beyond the scope of this question, so I will just leave this here. If you are interested, a question asking about paladin archers would be the place to do so.

Before everything else, I must warn you you can't play a "full tank/healer" in Pathfinder like you would in a MMO. It just doesn't work:

• The concept of a tank relies on keeping the aggro which is not part of the system

• A healer is supposed to heal nearly as much as the team is taking damages. You can't do that, or at least not for very long at all.

However you can play a character who is tough and can heal his allies if needed. Most of his actions during a fight will still be attacking (or casting buffs/controls).

Luckily the Paladin has some abilities that makes him quite good at that:

• You can wear heavy armors. It suits a "tank" and makes you able to get a very correct AC.

• Your lvl2 Divine Grace ability is really very strong. This alone is the reason why people are multiclassing Paladin 2. To make the most of it you will want to get as much Charisma as possible. It also means you will never need any feat to get bonus to saves (unless you want to make your teammates feel weak in front of you, but what is the point in this?)

• Lay On Hands is actually a very decent heal-during-a-fight ability. You can cast it on you close to freely (only a swift action, and you have plenty of uses of this thing) and the heal output is not bad at all. Using it on your allies can be useful but unless it's really needed you will often be better mauling the bad guy. Note that since it's a (Su) ability it you don't provoke any AoO for using it.

• Aura of Courage, Divine Health, Aura of Resolve, Aura of Righteousness, Holy Champion: Good stuff. No choice to do, just take the bonus.

• Mercy: It makes you able to heal conditions. It will come handy at some point. At 3rd level the choices are pretty equivalent. If you are playing with a barbarian take Fatigued since it makes a nice combo. Shaken happens more often than Enjoado but you are immune to fear so it will only be useful on your allies. At 6th level Diseased is only a solid choice if you don't have any other way to remove them. I would recommend Escalonado since it happens more often than dazed (and you can't un-daze yourself anyway). At 9th I would choose Envenenado and at 12th paralisado.

• Channel Positive Energy: This makes you better than a cleric at channeling, since you have usually more Charisma. Channeling during a fight is worth considering if one ally is below 0hp or if more than two allies are wounded. Be sure to keep some uses of Lay On Hands though. This ability can justify you to start taking channeling feats (you really have nothing to envy from a Cleric on that point). You can eventually spend some uses offensively if you happen to encounter undeads, but unless there is a horde of them you will often find you just do more damages by hitting them.

• Spells: You don't get much of them, you get them late, and you only know a small number of them. You will want to make them count. If you want a tanky feeling you can take spells like Challenge Evil or Compel Hostility (they are not really a good choice if you want to be very efficient to be honest, since they rely on saves from ennemies) or defensive buffs like Proteção contra o mal. There is a ton of good buff spells here and making a complete list would be too long. I don't recommend you to take any feats to improve your spellcasting (metamagic, school...) since it will stay a 4-level spell list and your feats will be better spent somewhere else.

The rest of your abilities presents very strong things (Smite Evil, full BBA, Divine Bond...) that you should not forget to use even if they don't serve your "healer/tank" build. Don't hesitate to hit hard: the easiest way to heal damages is to make sure they are not done and dead enemies don't deal damage (unless they are undead).

You can spend your feats to improve the Lay on Hands/Channel abilities, or just your martial abilities. You can for example go for the shield chain of feats and/or the mounted combat one. Spending feats to improves your saves is usually overkill. Improving your Initiative can be a good choice: at the moment I am on a campaign as a rogue and it happened several times that I had to delay my first round to let the Paladin charge first. Don't make your team wait for you.

Your alternate favored class bonus is actually not bad, even if it takes a long time before being noticeable, but since you have so few skill points I would better take those.

Archetypes have already been covered by previous answers so I won't insist on it. Some of them have good things but you usually come up with a more weak character in the end.

Tanking

While aggro isn't an explicit mechanic in Pathfinder like it is in many MMOs, there are still things that players can do to "tank", in the sense of preventing enemies from attacking their allies or encouraging enemies to attack them instead. Positioning is probably the most obvious - while the GM pode have a monster run past your paladin and eat the attack of opportunity to get to the wizard, I haven't seen it very often, and if they do you at least get the AoO. This is especially true if you build your paladin for combat maneuvers like tripping, where you might be able to stop the enemy dead in his tracks with your AoO (although it's worth mentioning that a lot of the larger monsters have very high CMDs).

Paladins in particular have access to spells like Challenge Evil e Knight's Calling, forcing the enemy to save or be compelled to attack you.

Yes, these things are more limited than the tanking techniques available in WoW - flying enemies in particular can be difficult to deal with - but depending on the level range of your campaign, what enemies you're fighting, and how your GM plays, they can work pretty well. Just make sure to have a backup plan for situations where the enemy doesn't want to cooperate.

Cura

While the others are correct that in-combat is fairly limited in Pathfinder, the Sacred Servant archetype does provide paladins with arguably one of the best options for doing so. Using divine bond for the +1d6 healing on channel energy means you're healing for 33% more than you normally would at 5th level, increasing up to 60% more by 20th level. Things get even better if you worship a god who provides a good channeling feat like Torag's Steelskin Channel.

Bear in mind that the Sacred Servant does give up a real amount of combat power for their healing, with no divine bond on their weapon and fewer uses of Smite Evil per day.

The OP question has been answered, I think, on what can (or can't) be done, to best heal the party, in and out of combat.
I would add two things:

1) Instead of Assimar, consider the Half-Elf as your race. From the Advanced Race Guide, the Half-Elf's Favored Class bonus is very good:

Add +1 foot to the size of all the paladin’s aura class features. This option has no effect unless the paladin has selected it 5 times (or another increment of 5); an aura of 14 feet is effectively the same as a 10-foot aura, for example. At 5th level, a Half-Elf will have a range of 15 ft instead of 10, for their aura of Courage. And at 8th, 11th, and 17th, other Auras. So, by 20th level, all 5 of your Auras will have a range of 30 feet! Worth considering, I think.

2) Choose a two-handed polearm as your weapon. Extra reach gives you AOO in a 15ft wide area. MUCH harder to get around you, and therefore fulfill your defender/tank mission. (You can also trip them.)