too thin on the river?

actually I put him on a 7 or T or 98 maybe, so i think it sucked

I hate checking back

not sure, what hands can i extract value from on the river?

By the river I don't really see anything you'd extract value from other than possibly AsT and the 89 missing.

99 and 88 too

river bet is fine/standard, checking would definitely require a significant read. make sure to note how he played this hand too that's pretty important info.

but, why am i betting river, i don't quite get it, why is it standard?

because the presumption is that 5nl player will call here often enough with worse.

when he donks flop from that position i personally have no idea what his range is but i imagine it's pretty wide, maybe not for this player but generally speaking. i guess the rationale is that by the river we have the best hand sooo often that even if most of the hands that we could hope to get value from are bluffcatchers, he's going to have bluffcatchers so often that the % he calls with them outweighs the times we value-cut ourselves. i think he can even have Kx (or Qx w/spade that peeled turn) because his fullpot flop lead looks pretty FOS unless he knows you have low c-bet, he could've just been leading flop w/overs or something. or just Tx w/spade that feels like he has to call river.

(i don't think Kx/Qx are a significant part of his range obviously and i don't "assume" he would lead air on flop, just saying i would account for some possibility of that because it feels like kind of a fishy lead in general)

also you probably don't have to worry about people c/r river with something like JT turning into a bluff

it's not like checking would be unheard of, i just doubt it's correct vs most. if nothing else i'd at least gaybet some small amount.