This guy is a super nit so what kind of range are we giving him when he calls preflop? 22-JJ, QQ+ is a possibility, AK/AQ maybe AJ/KQ. This guy isn't going to be calling much else from the BTN.
After the flop he could have a strong flush draw with overs but the turn and river eliminate those hands. His AF of 3 suggests he wouldn't check behind AK/AQ/AJ on the turn. He's not raising your cbet with KQ and probably lets his smaller pairs go as well. So my range for him after the turn check would be something like 90% TT-44 and 22 weighted towards the strong pairs, 9% QQ/KK/AA, 1% something completely random.
If he bets the river I'd give him credit for ten-high flush and better. I would just c/f the river and curse the flush gods. Betting is interesting but you're already ahead of most of his range and you'll only fold out a few small flushes and QcQs. Everything else you're behind calls or raises.