#1
Right now I'm really into Black Keys an White Stripes type of stuff and I notice that they would use feedback while soloing but I'm not sure they use it when playing chords and such, so I mainly want to know will players make use of feedback when playing chords, specifically power chords or sure you just make use of feedback when soloing
#2
I mean, I use it sometimes with chords, but that's usually for intros or closings. Otherwise it might be too much noise and distracting. . . but, hell,if you can make it work, or want to, don't be afraid to innovate.
#3
Like JelloCrust said, if you can make it work then go ahead and use it. Some people don't like that feedback sound but I think its cool. Cobain used to use it a lot if you ever watch his live stuff or listen to the Bleach album. J Mascis from Dinosaur Jr. uses feedback for chords/rhythm and solos. Sonic Youth, and My Bloody Valentine too.

I know you didn't ask for suggestions but...