TL;DR= Max value on river or x/c?

Blinds level; 50/100

Starting stack is 20k and as we are in the second level the average is still about that.
Two villains in this hand utg+3 and utg+4.
utg+3 has been playing quite poorly, over betting flops and playing fit or fold when facing a bet/raise.
utg+4 has been playing tight preflop but with a tendency to chase postflop. iv seen him get to a few rivers to fold to a third bet.

utg+3 bets 300ish
utg+4 calls, cutoff calls, buttin calls, sb calls, Im in the bb with K10ss and call.

Pot; 1800
Flop; Js 9s 7d

sb checks, i check, utg+3 bets 1650, utg+4 calls, co fold, btn fold, sb fold. I call.

Pot; 6750
Turn; Js 9s 7d Qh

I check, utg+3, utg+4 calls, i raise to 6k, utg+3 folds, utg+4 calls.

Pot; 9162
River; Js 9s 7d Qh 8s

I check, utg+4 bets 5k and i call.

I opt to check/call the river as i think his value betting range is weighted nearly always to the nut flush and obv Q8ss beats us too. By betting the river we do get called by all worse flushes, and maybe straights not made until the river. His flush draws that made it to the river are heavily weighted towards the nut flush as i have two Broadway spade blockers and with whats on the board it leaves combos of AsQs, or As7s-A2ss, Qs7s-Q2ss and low suited connectors.

He shouldn't have Qx very often here but if he did decide to see a flop then its not unreasonable to think he stuck around until now following his tenancies. however he more often has Axss.
I would say that considering the cards we can discount, he even more often has 2pair, sets and straights, but i am sure we see a raise with any of those hands before now. He certainly isn't calling a river bet with 2pair or sets.
He perhaps calls with a A10 or 9 10, that made a straight on the river.

My check call was based on me concluding that if the majority of the hands i get called by here beat me and i fold out the rest, i can check and gain value from when he bluffs a worse hand or value bets a worse flush. villains stack isn't enough to bluff after i bet and i am obv never folding.

Should I re-raise all in considering villain only has about another 6k left behind?

I feel its close and not a big mistake either way but it has to be said that at the time my gut was thinking Axss, and im not one to see monsters under the bed. Do you guys go for max value here?

(ps. i dont mind posting results after some discussion)