UTG is a 37/16 fish that doesn't fold to 3bets.
BTN is a 64/28 doesn't like to fold vs 3bets (30%) and he cold called a 3bet 2/4 times.
I expect both player to have really wide ranges

I should bet bigger I know, probably and stack off any turn (probably?)

BTN can have AK and K9 pretty easily. I don't expect him to overplay many hands especially in a MW pot, JJ is likely, JT is less likely. I don't think he could have 33 often, since he's raising 5/19 times OTF, and we are MW so I think he would be somewhat scared and raised the flop. I guess most of you are stacking off but how many times are you good here?
Obv If I sized up more on the flop, the turn would be easier to play and probably would yield higher EV due the inelastic flop calling ranges