After how the action went, OTR Villain's raise is really strong, and the way the hand played, his value raising range is very heavily weighted towards sets. I would just call river, I don't see him raising river with a value hand that you beat.

The villain's hand should be so heavily weighted towards value hands because your two spades are blockers to his most frequent types of bluffs.

The river turns into pure silliness - we're basically turning our hand into a total bluff when we re-pop him because I really don't see what he would call with that we actually beat. I wouldn't expect him to open hands that would river worse 2 pair hands, namely T8 and 86.

So I guess all that being said, do people prefer a river check and let villain have any type of bluffing range?

Agreed, river is bad. I appreciate the feedback.

I guess in hand I didn't think he had a set since he checked back twice with a flush draw on board (which I won't have very often). Is this line of thinking wrong? In general is check/check/raise like this usually strong?

Other than that, what do we think is the best option on the river? Any reason to lead the turn?

Especially after he raises so small OTR, yes, this line is usually very strong. OTT is the best time to bet imo. You get value from all his Kx, FDs and low PPs. If you have no reads on villain, I think I would still call. If he is a weak player he might be overvaluing Kx, playing AA in a weird way or randomly throwing a bluff. I am not sure these are enough reasons to call, it seems a bit of a stretch of the imagination.

Agree that we need to bet the turn here. This is for value, protection, and information. We're getting called by worse a lot of the times and this is a draw heavy board now. If he calls we can narrow his range down and re-evaluate rivers. If he raises we have to proceed with caution.

Ok, so lets say we lead out small on the turn maybe like 750ish and he raises small to 1650ish or even min-raises. Do we call turn and check/call river? check/fold river depending on bet size?

Spoiler: He had 66 of all hands.

I would call his turn raise, since I would expect all his really strong value hands to always bet turn, so I would be a bit skeptical about the turn raise. He might also be raise KQ and AK. I would probably call river too for the same reason.

I like the turn check, the king hits his check back range and is a card he will delayed cbet often. On river I think just bet calling is the only way. When he raises and you reraise and he comes over the top I don't think people bluff like that and that he has 8s which make sense the way he played it.