Question 3: What hand(s) can Hero 3-bet here that will have the most fold equity?

Obviously we want hands that block villains continuing range here. I havn't done the math to figure out which hands block the most, but only simple math is need for that, so here is just a list of blocking hands.

TT+AQ+

A VERY basic assumption to be made by this is that the best FE comes from holding cards that villain will continue with. I may be just stating or restating the obvious, but that seems to me, a very simple thing to remember, and build from.