I can see many value hands in his range, you don't beat. I think it is a two part process on the river. Figuring out what your equity is in the spot and the required equity you need in the spot. It is up to you to find his bluffs on the river, I think there is a ton as value there with only this range as value for 3-street barrels. I don't know how wide he is preflop but based on the assumption that he stabs a lot it could be a regular with decent stats, but it is not given in your decription of the hand.
The value hands.
56s, 78s, 89s, TJs, 44, 77, 88, 99. approximately 24 combo's. Let's say he doesn't have the K8, K9, K4 combos. Also we are not totally sure if he does play all the combo's given this way, might be he sizes up when hitting straight or going all in with them on the river. We seem to have no read but probably he uses this kind of bet sizing with his value range.
I don't see a ton of one pair hands that are tripple barreling here. The 8 got scared of the 9 and K etc.
His sizing is not just on the flop is 75% or so. That concludes that he is probably leaning toward value or semi-bluff. Without reads that he is spewing off partially stacks like this with some random bluff. I would be inclined to fold with the line chosen by hero.
We need on the river. approximately about 30% equity. Against his 2-pair plus value range we got approximately 0%, if we however can find a Kx in his range that continues bluffing on the turn I can see some worse value hands and we can get the 30% with some bluffs reasonably well.
If we can find approximately 8 combos of stone cold bluffs we should call.
