I'll try to answer your questions. If my language is not clear let me know and I will restate what I say.
- The Armor of Bones does not stack with the Full Plate Armor. Both grant an 'armor' bonus to AC, and because these are the same types of bonus they do not stack with each other. If you use the Armor of Bones ability while wearing armor, use whichever bonus is higher.
At 15th level the Armor of Bones will grant a +10 bonus, which will be higher than non-magical full plate armor.
Note thought that at 13th level, the Armor of Bones will also grant DR 5/bludgeoning, which is a very nice benefit.
- Death's Touch will deal 1d6+6 damage for you right now. This is pretty much the same as an Inflict Light Wounds which does 1d8+5. Death's Touch will not deal as much damage as higher level inflict spells, so those will be better. But it will be better than Inflict Light Wounds, and doesn't use a spell slot to do it. Note also that if used on undead it grants a +2 channel resistance bonus for 1 minute, so if you have friendly undead it can help them a little.
Also note that both Death's Touch and the inflict spells will benefit from the Bleeding Touch revelation, which will make both of them much more dangerous.
- "Raise the Dead" lets you summon a single skeleton or zombie under your control, but only for so many rounds (equal to your Charisma Modifier). Right now you could make either a Bloody Skeleton or a Fast Zombie. The skeleton or zombie will have 12 Hit Dice.
This ability is somewhat weak, in that if you are in a fight appropriate for 12th level characters, a 12 HD zombie or skeleton will not be much use. It will have a hard time hitting most things, and will be destroyed pretty quickly if its targeted by most monsters that you will fight.
The benefit is that it disappears after so long. This means that you don't have a skeleton or zombie following you into cities and towns, which would normally be a big problem for most city guards and townfolk.
The "undead servitude" ability gives you the Command Undead feat for free. At 12th level, this lets you bring up to 12 HD of undead under your control, and the undead failing a saving throw (the saving throw DC should be rather high for you since it is based on your Charisma). Using this ability depends on there actually being undead around, whereas Raise the Dead will simply bring one into existence. Command Undead will also let you keep the undead under your control for a long period of time. Intelligent undead, such as vampires or wraiths will get a new saving throw each day to break free of your command. Unintelligent undead such as zombies or skeletons will remain under your control until they are destroyed, you release them, or you command more undead than your level allows.
Command Undead benefits from being able to take control of stronger undead such as vampires or shadows. It also allows you to keep them under your control, but this can be a drawback if you travel with good-aligned party members, or try to take them into most towns or cities.
I would generally think Command Undead to be stronger. But Raise the Dead would be easier to use.
- You can only create skeletons and zombies with the Animate Dead spell. You will need an actual corpse first, the undead are not created out of nothing. Generally, the bigger and stronger the original monster, the stronger the undead you Animate will be. Thus, you generally want corpses of creatures that have high racial HD, such as dragons, or large animals, such as many dinosaurs or an elephant. Creatures with many natural attacks are also good choices, such as dragons and hydras.
You can make up to 24 HD undead with the spell (twice your caster level). If the area you are in is under a desecrate spell, you can double this amount (48 HD). However, you can't make any skeleton from a corpse with more than 20 HD, but Zombies don't have this limit.
You can choose to create any of the following types of undead with Animate Dead: regular skeleton, bloody skeleton, burning skeleton, regular zombie, fast zombie, plague zombie. If making a bloody or burning skeleton, you count their HD as twice the amount; thus, making a 10 HD bloody skeleton counts as making a 20 HD undead with the spell as far as how many undead you can create per casting, and how many you can control with the spell. The fast zombie and plague zombie count the same as normal.
Probably the best undead to make would be fast zombies. They will have good attacks and damage and decent hit points, but they won't have the DR/slashing that a regular zombie will have, and like most zombies their AC will not be good.
Bloody skeletons are also a good choice because they come back if destroyed (unless they are destroyed by positive energy or in the area of a bless or hallow spell). But because they cost double the HD to make, they will be weaker. But if you want them to stay with you for a long time, they are a good choice for that.
I would generally go with fast zombies from dragon or hydra corpses if possible.
Again though, you run into the problem of travelling with such creatures, as most city and towns will not look kindly upon dragon zombies coming into their city.
Hope this all helps.
No, neither of those abilities has a Saving Throw.
That rule about saving throws is simply to state how the saving throw is calculated for those oracle mysteries that do have saving throws. Look at the Flame oracle's "Fire Breath" and "Firestorm" mysteries, or the Heaven oracle's "Interstellar Void" mystery. Those make effects that have saving throws, but don't state how the saving throw is calculated. Thus, you go to the rule about 10 + 1/2 oracle level + Cha mod.
If the mystery doesn't say anything about a saving throw, then it doesn't have one.
The only Bones mysteries with saving throws are "Undead Servitude" and "Voice of the Grave," because both of those grant abilities that already have saving throws. (the Command Undead feat and the Speak with Dead spell.)