1: I can't remember. Maybe someone else can answer that one.
2: It could differ from game to game; I'm not sure. But my general understanding is that human souls don't become angels or demons. As far as I can tell, if someone leads an acceptable life (according to whatever determines that), they simply reincarnate. If not, they end up a prinny as punishment, and work their way (via salary and/or good deeds) toward being reincarnated. I assume that how hard it is to attain reincarnation is determined by whether they are sent to Celestia or the Netherworld. And I also assume that which place someone is sent to is determined by how they lived their lives.
3: It appears to be a mixture of both. I can't say for sure how good deeds would be tallied, like money can, but at the very least earning money seems to be required. That's why they wear those pouches, if I remember correctly.
I wouldn't really rely on my information. I'm mostly working from memory, after all.