To address in order:
1. All gods, titans, heroes, etc. used in this RP will be interpreted from the versions of themselves represented in the olden Greek myth.
2. Even though they can't be used in conjunction, they can't be the same strength as normal God Bursts. That'd be a bit much.
3. Hades is the god of the underworld and shambling corpses for the most parts. Also riches, like minerals, gold, gems, etc. Rocks. Shadows. You could do something pretty cool with all of that.
4. I'm not referring to God of War Kratos, although he is based on the ACTUAL Kratos, the god of strength in Greek myth.

[s]also cthulu's an elder god from lovecraftian myth, jussaiyan. |D[/s]