We only have ~15 hands on BB, he has played 3 of those.

I'm not sure about my check here.
I think villain's range when he calls the flop is likely pp's, Kx up to KQ, strong Ahi, some fdraws and some combos of 22/44. I don't really think most of those hands are folding to a turn bet. I also think the flush is kind of deceptive and we are in position on the river so if villain has a strong hand like Kx, he will likely bet and we can raise large for value when we hit.

On the river we have another decision. Villain's range is now a lot weaker. Kx or better is mostly discounted after checking turn and river. I think he's probably almost never checkraising this river.
He might have JdXd, missed fdraw, strong Ahi or pp's. The question is then whether we think he will fold more of stronger hands or call them.