Let's see here:
1) Approximately? Hunters have been around a touch under 10 years. The transition has been going on longer, but Hunters really have only been needed as of recent as protests have become violent.
2) Both! That said it's not really faded to the point where Magi can't use magic, but certain regions have a notable decline in energy.
3) Nah, play whatever you want! All guys, all girls, whatever happens, happens!
4) Roughly speaking, yes. But that changes based on lifestyle - Dimurans die in combat constantly so that tanks theirs. Divine excel at magic and can prolong their lives, Murad technology and Ydra medicines grant them both longer lives. The Varuna are probably the closest to the "average".
5) Gold! Well, and silver and bronze. Coins really, kept it simple!