6 handed No HUD stats

HJ open to $1.75 (from $62 stack)
CO Villain 3 bets to $4.25 (from $100 stack)
Hero on BTN 4 bets AA76 to $15.25 (from $130 stack)
Blinds fold and HJ folds, Villain calls.

Flop Q97
Villain checks, Hero bets $16 , Villain re-raises to $81, Hero folds

HJ was a fishy player who played to many hands and made some pretty light stacks off which were pretty bad. So I think there may be some merit to flatting preflop to keep HJ in, also would keep the SPR slightly higher than if I 4 bet.

CO was a Russian reg who was 4 tabling, was playing pretty solid and well in general, I presume he would be 3 betting the fishy HJ player fairly wide to isolate and play HU IP against him.

Main questions are should I 4 bet here or just flat call ? , also on flop is bet folding better than just checking back on flop ?

I mean what hand are you trying to get value from, exactly KK? Any pair with an open ended straight draw is ahead of us. Any pair with a gutshot is flipping. Rundowns are ahead. We block one of our own 2 pair outs

I prefer to check back and decide.

I think you gotta put it in after betting flop. I mean you need what, 25%? (I suck at figuring out the precise math in this spot but looks like 25)

Bet/folding burns away soo much money

Optimistically hero has about 33%ish equity against reasonable range, so given his sizing and villain description he should fold, I'm not a big fan of this line as almost everything villain has besides kkxx connected ok with this board

B/f half pot is the 2nd nutworst option if we have only 1 higher betsize on the flop.