river bet size when I am ahead

25 hands just means he's unknown, I might get my own stats to be 34/28 if I have a hot-start or 11/8 with cold start after 100 hands...

Feels much like he had something like an OESD, gustshot or overcards (broadways) with his flop donk. Might be A2 or A8 but that would bet bigger on turn. Might still have some mid PP's he's playing badly.
So only value you can get on the river is from these pairs, maybe a T9 or ATo. This I would do with a 15-18 BB size. More likely to get a call from these hands and when re-raised it's an easy fold (would assume he has sets in that case) if it's a click reraise I might call.

I would raise/fold flop I think.

On river, what will call? Turn raise is super nice, could easily look like a bluff, flushdraw, or he could have a flushdraw himself. Maybe he was hoping to call turn hoping you check back river. If you rep bluffraise on the turn to now get call from Ax on river, the sizing is nice, he might pay you off with Ax. But he lead out the flop OOP, so looks more like 9x, 8x or maybe JT. I think to me it mostly looks like 9x or 8x that put you on bluff on turn. For that he is not going to call of course 2/3 pot if he is not that fishy. So let's say we think he has J9 which could be true. How much would J9 call for example? If you bet really small, it would look like a valuebet though. So I think it's a nice bet, maybe 20bb river to get more calls but it would then look like a value hand?

Seems well played I think. If you raise the flop there aren't to many weaker hands villain would continue on a dry board like this.

The rest seems standard. Maybe you're bet could be smaller, but if villain missed a draw you can't get any action anyway.

Cheers,
SDK1987

I think it's fine. You could raise flop but it is mutiway so flatting is fine.
I personally think you could go bigger on the river. When he doesn't jam and everything bricks he could have two pair or not want to fold an ace.

25 hands isn't enough to make any assumptions