Will strength and character supremacy dictate how a monster dies? (The stronger the character, the more the monsters explode, fly off the screen, etc.)
Acid, they have stated that when you get a critical hit on a monster, it has a different death animation. Also i'm pretty sure they have multiple regular death animations for the same monsters.
4. What sort of base customization (other than female) can we look forward to?
They have stated that there will be none other than picking male or female at the start. As to whether there is going to be anything other than getting different gear, I don't know. I'm pretty sure they also mentioned they weren't going to let people dye things (though they did kind of in D2, with gems)