I always provoke 3 turkeys together. Can do more, but 3 is optimal for me, because if I provoke too many, I might not be able to get close enough to loot. And 3 allows me control the damage they do to each other.
As to your other questions -
1) Peace on one provoke
Avoid doing this unless 1 of the turkey has significantly more HP than the others. This will stop the peace'd turkey from damaging the others.
You want them to die as quickly as possible (at relatively the same time). You can use it as a form of damage control to make all the turkeys you provoked have roughly the same amount of HP remaining. But even so, provoke works better.
2) Discord on one provoke
The discorded one will have lower resists and die much quicker than the undiscorded one.
It will also have lower strength/wrestling/tactics and thus do less damage to the undiscorded one.
Note: Normally discording mobs lowers their stats which indirectly lowers their barding difficulty. But because the barding difficulty for the turkeys are hardcoded and not tied to the turkey's stats, a discorded turkey's barding difficulty does not get lowered by discording.
3) Discord on both provokes
Yes, do this to ensure they do max damage to each other.
4) Health of the respective creatures
Does not seem to have much impact to their damage output. They do not have a HP based "firebreath" attack.
To control damage, you provoke a->b, then b->c, then c->a.
Most of the time, this will result in a nice triangle where each of them will be biting another's tail. All will be taking damage equally.
Once you have the chain started, reverse the chain, provoke a->c, c->b, b->a.
This will ensure that they have all aggro'ed each other. This is important once the first turky dies. Coz you want the remaining 2 to keep at each other's throats instead of yours.
Now, watch their hp, anytime you see 1 of the them being beaten down too quickly, provoke the other 2 against each other and take the heat off the weaker one. Anytime you see one having significantly more hp, provoke the other 2 on it.
Hopes that makes sense. Good luck!