Game is $2-$100 spread limit.

Villain is an old guy, just seems like your average bad fish. Limps in too much, calls too much, doesn’t get enough value, etc. He has a stack of $600 due to coolering a kid with Ac6c vs KcTc when a third club hit the River on an unpaired board.

Hero covers #humblebrag.

Hand: there are two limpers, and Villain raises to $10 in the CO. Hero 3-bets to $30 with 8d7d. Everyone folds to Villain who calls.

Flop: Js7s5s ($64)

Villain checks. I bet $18 (low, just to fold out his hands that are absolute airballs, 4c4d or AhTh stuff). But he calls.

Turn: Js7s5s 9h (Pot: $100)

We’ve picked up a two-way straight draw to go with our pair. Villain checks.

What should Hero do?

I wouldn’t reraise an OMC like you said.

If he’s loose and passive he has you crushed preflop.

Check back flop with no spade in position.

Check turn

Evaluate river

Being in a spread limit game makes 3 betting with drawing hands generally bad. You need to be able to steal a lot of hands for it too work. As played the flop bet is OK and on the turn take your free card. Your not trying to build a big pot, your hand has just enough show down value that you want to see. The last thing you want to happen is that you bet and villain raises.

Probably not 3-betting pre, just prefer to call against this type of player and raise all my premiums. Think I'm going to be mostly checking back this flop without a spade. AP I check back the turn and see what he wants to do on the river. We have decent showdown value against a lot of his unpaired hands drawing, and if we continue betting the turn he is going to call with almost 100% of them. If a fourth spade peels off easy fold, if not then he will just check his air and we are good a large portion of the time.

xb turn for sure.

I think PF is good is Villain has a history of folding to 3-bets. However, you say "calls too much" which I expect extends to PF action, too. In that case, just call PF.
I like flop bet for the reasons you describe, but once he calls, you are likely behind. Take the free turn card with gratitude. Check back river unimproved or maybe call a small bet. Obviously bet/raise if you improve on river.

Check or bet your entire range for 1/4 to 1/3 pot. I prefer my whole range two streets in position for around $25 into $100 there. It works more than the 1 out of 5 times you need it to when behind. And when you have a monster sometimes bad fish will,nterpret the range bet as weakness. I like your flop sizing.

River inyour game if No c/r by villain Im only betting with your hand if a 7 or 10 comes off. Unless they have seen you 1/4,1/4, big bet with top of your rqnge in-the past. Anyone willing to call two small bets either has a big spade you maystill be ahead of, or a hand unlikely tofold for $100 in a $150 pot.

RESULT: Hero reasoned that he is still ahead of Villain’s AsKx / AxKs / AsQx hands—and isn’t in terrible shape against his AxJx hands—and decides to bet 1/3 pot again ($35). (He also reasons that IF Villain flopped the joint, by betting again on the Turn he reduces the likelihood of facing a $100 bet on the River, as Villain will let me keep bluffing.)

Villain called.

River: Js7s5s 9h Tc (Pot: $160)

Well it’s better to be lucky than good.

Villain checks, I bet $100, Villain snap-calls with…..pocket Jacks. Sorry dude!

Flop sizing is horrible.

Tiny range-bet on monotone flops is GTO-standard. What do you think it should be?