You might want to send them an email, I have seen other members get banned because of low quality traffic.
traffic from myspace links should not be a problem, however traffic from myspace bulletin spamming should be and i'm sure IS against the TOS. if in doubt, email Adsense Support..
Seems like it shouldn't be a problem since Google's running their own advertising all over MySpace. If it's good enough for them...though I would stay away from any mass/automated posting. But that's a good general rule for any site.
Logical, but possibly wrong. Google prohibits the average publisher from doing things (like putting adsense on adult oriented sites) that Google will do itself, or allow premium publishers to do. Read the TOS. If in doubt, email Google before you do something.