1) Big sizes are usually used to leverage a nutted hand advantage in a polarized betting strategy. Here we're not fully polarized (we're betting also 9x or worse), villain has more 7x combos than us and having trips has a significant removal effects on our opponent's calling range -we cannot target overpairs, they can with x/raises-

2) It depends on how relevant the busted FD blocker is relative to the range that checks back the flop and calls a turn probe. With tight UTG-MP ranges and the As being on board, KJs, being a straight, Qxs being a pair, it's hard for us to just have naked hearts, so in this case I would say blocking hearts doesn't matter much. On a 9 7 2 4 3 runout things are much different, as we can have a bunch of Axss and suited broadways, therefore bluffing combos without busted fd blockers is going to perform better.

3) No, set mining is not profitable with that SPR. Sometimes we will play it aggressively, other times we're trying to get to SD. The EV of the preflop call is very low, a little better than BE assuming reasonable 4betting strategies -if we're sure villain is massively underbluffing we can consider just folding pre-. If we fold we lose 11bbs, so if by calling we make more money than -11bb100 (even -10bb) calling is profitable.