Never folding given the pot odds and the guy you describe.

Make it bigger preflop given stack depth and the described line up.... Like WAY bigger.
As played it looks like a fold river... Snap call turn when it really seems u have a
monster, then donk shove river.... So rare to be a bluff. Many spewtards would not spew using that line Im pretty sure. In general, when a player plays passively on the turn facing an agressive action (can be a bet that he calls, or he bets and calls a raise), then suddenly decides to donk shove the river...these are the nuts baby. The river also improves 76, which is a hand he could snap call with turn...
Ive called hundreads of times in similar situation, to be shown the nuts 95% of the time.

what jambonbeurre says.

Snap call. Altough he can have 76, which I assumed he had otherwise you wouldnt have posted the hand. Also, you can bet wayyy bigger OTT, like 2500 min.

I agree with betting much bigger ott...
Result is I folded, my thinking was pretty much in line with MrSneeze's post. Having played with villain some more since then, I dont believe he would bluff jam this spot enough to justify a call.

Point taken on turn sizing however, half pot is way too small.

Where do you find game like this dude ? :) Spewyfest playin 350 deep in 2K NL haha

It pays to travel the world jambonbeurre :)

yeah it's an egregious error to not raise more pre.

As played on turn, I would not be folding to, and I quote, "Tilted spewtard" haha. If he has us beat, ni han ni han. Other wise, scoop.

Interestingly, you praise 'GTO', but eventually your reasoning is basically: 'lol I have overpair, not folding because vilain is loose'.
Which, surely, is not an 'optimal' reasoning on this particular spot.

We are super deep (effectively less because of the preflop action, but still, pretty deep). It would be a severe mistake to limit the thinking process to the preflop tendencies of our friends at the table... As much as players might call liberally 500 preflop, doesn't mean they'll shove 5K river using a line that clearly indicates they're likely to have something strong (strong enough!).

The 'GTO' approach here, as in every spot, is to play 'optimal' based on the elements we gathered (the information, the data... because it's live, the reads as well). Optimal here is to embrace and deal with the complexity of the spot. It is NOT stacking off any board merely because we hit a big hand preflop.
If we do that, we basically make the spewy strategies of our opponents profitable (they may well play way too loose and bad, and station... but when they hit we pay them off, so they must be right to play every hand!).

did villain show the hand?

The reason you can't apply GTO in this spot is b/c you can't even solve for it OTF (we're multiway). Which renders the entire GTO discussion irrelevant. If that's not enough, our preflop 3bet range here is already night and day from GTO.

@seven and sneeze: when "GTO" stops clouding the discussion, you're both going to be in agreement that it's valuable to understand how a more simplified scheme of betting options can allow you to play a more well balanced strategy -- regardless of whether or not you choose to exploit from there -- knowing the balance points generally gives your exploits more versatility on the fly. The GTO argument is not a well balanced thought process to be using in game or even in post mortem analysis, simply b/c it's usually intangible, which makes it irrelevant to approaching higher implementable accuracy. You can still be effectively balanced without being GTO. You can also discern more relevant exploits when you're functioning from a simplified model of balance.

Villain's play is highly imbalanced. If we have a high enough confidence of where his imbalances are (which we should if we're labeling him a fish), we should flood in with the hard exploits. By the flop we're likely incentivized to deviate so far from a balanced strategy that idea of balance shouldn't even resurface unless we suddenly become clueless on a future street of what villain is doing, in which case we can hopefully rely on playing some sort of recovery MDF with our already imbalanced range.. if he does something like jam river or whatever.

He spaz peels turn. I agree we should be using larger bet sizing here, villain probably has no idea what the size of the pot is give or take $500.

He open jams river on a card where a lot of his gutters pair, he improves to a significant amount of straights, and some hands make 2 pair. He's drawing from a rainbow flop. Right away that needs to register as a range that polarizes unnaturally with too few bluffs. Meaning my confidence interval assessments of his player type need to converge to "through-the-roof-aggro" before i bluffcatch this river -- and i agree with whoever said that if that was actually the player read, that we're much more likely to see him take an alternate bluffing line (like a XR line) at some point in the hand, given his equity distribution on this flop/turn, and given the ~universal environmental trends for aggro-fish tendencies.

If you expand your context of GTO to realize that the only relevant takeaway from it as a player is "how to approach simplified, well balanced play", then the next step you can take from well balanced simplifications is: "how do i apply confidence intervals to villain's possible strategies, based on his tendencies, to arrive at a more inclusive, less bias assessment of his actual strategy". Point being the most "balanced" assessment yields the most relevant strategy, where relevance could be defined as "that which becomes incentivized from the most inclusive/unbias viewpoint available". In this case the most "balanced" assessment is highly exploitative.

yea basically b/c solver can't run multiway pots