Reads: He once opened QJs UTG for $5, got called only by the SB, then bet middle pair on flop and turn (he turned an OESD too though). He once bluffed with A4o (see my other thread). He hasn't gotten out of line other than those times...seems to have a normal preflop looseness and fairly normal postflop aggression factor.

One player limps. I limp behind with K9 in the hijack. The CO and button are really tight/passive preflop and unlikely to isolation raise. Also, I'm pretty deep against most of the active players + the limper.

Folds to villain in the BB who makes it $5. The limper and I both flat. Flop comes Q98. $190 or so effective. Villain bets $15 into $16. The other limper folds and I flat. My reason for flatting is there's a chance he's just c-betting AK or AJ. Turn is 10 and villain checks.

Turn a made hand into a bluff? If we bet, do we continue with a huge river bluff?

I mean, If you are going to bluff here OTT, I think you need to follow up with a river bet too when the board doesn't pair seeing as you seem to think he's usually got a strong one pair hand here or a set that probably wont release here on the turn. But I usually wont try to bluff players if I think that that have got top pair of better. I just check it back, since I don't really think that he has that narrow of a range and your hand may be good now.

Sry but playing that hand pre with limp/call is -EV u sure.
Flop is still a fold dont know what u think but cause u find 2 hands in his range that he might Cbet that you can beat u are still behind of his range. Even if he has these two hands he equity. Dont know why you want to get into this spot where u play for stacks with that hand. As played i would still just give up and hope we have him beat here. River should go c/c most of the time. Maybe he really have AK or a PP here and we win the pot.
But i hate your play.

i fold flop. only reason i'd float is with the intention of stealing on a later street when scare cards come or if V cbets at too high a frequency and will c/f later streets.

Yeah I definitely bet here. There's a good chance he can fold top pair or any one pair hand on this board.

The only way I wouldn't attempt to push him off his hand is if I have seen him regularly slow play his nutted hands. Like check/call turn check/raise river. That would be worst case.

Barring a read like that though, I think this is a good spot to turn up the heat. You can rep 2 pair or a straight no problem.

If he does call the turn, I'm trying to get some kind of read before I bomb the river(though admittedly I'm looking for an excuse to follow through)

club rivers would be interesting. Say he check/called turn, checked river. What would your play be in that spot?