Hi there Siereis (nice palindrome),
I can certainly answer some questions,
1) correct, it's a battle for him but in the grand scheme of things it's more about fulfilling more wishes (and more quality wishes) for your side than for the other. These 'life long' wishes tend to bring in more in the long run than more short term (ie I wish to be rich), which is why they are granted (since removing a wish granter from the wish fulfilling game seems counter productive). I'd say mind control is off the table, as is banishing the other side. Seduction, great...finding legal loop holes also good (if 30 days is coming up and it looks like your side isn't going to be chosen, try to invalidate the trial so you have to go another 30 days...and so forth), things that can cause wacky hijinks are also good, otherwise I don't know if I can think of anything else that would be off the table. Chaznia, since you are also playing do you have any other ideas?
2) I'd prefer no mass murdering psychopaths, I'd say if you are chosen to be one of those granted access to fulfill wishes you can be civil and don't cause many issues on a global scale just for a whim (It would probably cause the other side to hunt you down, and may cause your own side to pull you back to preserve the balance).
3) I'd say when they are with him alone (or alone with him and their rival) they can look as angelic and demonic as they want, but being discovered by the outside world is probably bad. I'd say the general populace of people not being played by us, can be a little on the ignorant side when it comes to any spells cast out in the open provided they can be plausibly denied...
I guess I'm looking at this as being less a gritty realistic game and something more light hearted and fun like the original source material.
I hope this interests you Siereis, either way have a great day.