yes and no, yes, you can technically, no you should not , until you start to get some REAL traffic, genuine.
scrapers get banned from adsense, so NO. Adsense requires unique content. Why not just read the guidelines?
Of note is that a CTR of around 1% is good for a forum, so don't expect the adsense revenue to change your life.
you can but not recommended unless you want to loose your adsense account. trust me, Adsense is the best PPC ever and you can earn a long term income from adsense.
No you cannot use that for adsense because adsense do not allowed for copied content while google's other products are banned for copied content. I use copied images from other sources so google delete my blog for that copied content for my blogger account and this adsense account has a economic relation so adsense banned for it. If you use your account for that purpose then your adsense account will be deleted.
Yes well you should not use any kind of content from other sites/blogs, otherwise your account will be gone.
Adsense forum can use at forum but you should abide their rules regarding copyrighted materials. Your account might be disabled and if that happens you're not eligible to participate in Adsense program.
apply adsense in a blog with unique article. and once approved by google you can use that code to your forum