Is it possible this player is playing As 9s ? I'm pretty sure you would have gotten a re-raise if villan had KJ. I'm pretty certain by the small calls I'm putting him on middle pair on the flop with a flush draw.
QT would have re-raised the flop
KJ would have re-raised the flop
I only see a suited ace from here, I think it's definitely going to be a chop.
The c-bets gave him just enough to start chasing especially with the bet ratio on the turn lowering gave him more pot odds
to try to draw out.
No way he has much of a hand it is possible villain has QJo but that board is pretty ugly and scary to bet into without a free rolling hand such as Ks Ts, which shouldn't be in his range either. But I smell As 9s
Ks Ts would have been a 2nd hand I could possibly put him on but not KTo.
I'm saying 25%-30% pot value bet on the river here. IMO... I may be wrong but I honestly believe that it's a chop on the river and you were way ahead until the river.