Not sure he’s only repping a set (you mean a trips or fullhouse?).
He might have 6x (but the check back on the turn is a little odd). I think I would call here with aces, mainly because our hand is underrep, we played it super deceptively. Villain might be bluffing the river with T9, thinking you have AK, AQ, KQ and missed. I suppose he’d called with a Jx, maybe 8x
I think I call, but knowing we’ll lose some times.
Also, I would’ve played it differently, id cbet flop and prolly turn too. We don’t know villain but being IP vs 2 players he can be there with mid connectors or gappers, so I think there’s a bunch of Jx and 8x in his range (6x are possible too). I’d bet tonget value from his lower pairs and gutshot combos, such as 98, 87, 75, 97, T8, JT, QJ, J9 etc