Could I have found a fold here?

Probably tough to find a fold unless you have some specific reads on him. I mean, that hand makes the most sense for that line here, but trip jacks is probably too strong to fold.

I'd probably bet bigger on the turn for this reason, specifically because you're going to have such a hard time folding if the straight or flush come in. 12k is what, less than half pot? I'd use a smaller size on a board that was more dry and unconnected, but here, I'd prefer to go ahead and really charge any draws or put Kx in a tricky spot. (Or maybe even stack JdTd whenever he has that.)

Bet bigger on turn. You’re likely to get called anywhere up to 2/3 pot with a flush or OES draw but at least you get some Sklansky $$

Fold to river bet which is never a bluff in this spot.
Unless it’s a missed flush draw in which case you should call.
Or it’s a worse Jack maybe, so definitely a call.
Or it could be KJ/J9 so fold.
Or it could be Q10 ….

Posting outcomes leads to poor analysis.

Not taking ICM into account we need to win this hand about 1 time out of 4 to make the call profitable. So I guess we have to call against a strong player. To call against this player we have to believe that he will bluff his missed flushdraws once for every three valuehands that also bets this river. Will he do that? I guess the answer is: He might very well do that, but we don't know. The fact we haven't seen him being much active is not much of a proof. He might have been card dead. And as we all know some players that aren't that aggressive or bluffy under normal circumstances sometimes executes bluffs in spots we wouldn't have thought they would do. Something like this was his 4th or 5th chased draw in a row that missed could have lead to tilty, bad river bluff.

In the heat of the moment I think I probably call the river, but not with a good gut feeling. But against many players I think this in fact is an exploitative river fold.