Flop bet - absolutely. Two reasons: thin the field, and add some value to your strong (yet hidden) draw.

Turn: raise and don't stop. At this moment you have the nuts.

River: I'd call. UTG's turn bet could mean he has something less than a flush (a lot of people don't raise KQ PF), he probably has no idea you've made a straight, and you're getting 8:1 odds.