You have better hands to call down, because of 2x pot you are fine folding a bunch. This combo has bad blockers for a bluffcatch cause of the 6s. Villain value range 33,KT,AJ,J9, try to block those. You will have some AJ,TT,Kx yourself and can consider bluffcatching with like QJ no spade would be a better consideration.

River is a superclear fold. Calling is a very big mistake. I'll give you a bunch of reasons:

Basics & Pool tendencies:

• He overbets turn and river, so his representing super-strong value.
• The average player in NL2 severely underbluffs when taken this super-strong lines.
• You have no evidence that Villian is a super-mega-aggro fish.
• You have a pure bluffcatcher against an underbluffed line, so fold.

Game Theory:

• The optimal strategy (GTO aproximation) will defend on the turn, but fold on the river vs the overbet, in fact he folds strong hands like J9 (straight) and KJ (trips).

And more subtle data if you think he might be overbluffing:

• You are blocking busted flush draws, wich is bad for bluffcatching, he doesn't have more natural draws except for stuff like J8s-J7s (is he really overbetting that?).
• He has KQ, KT, 33,AJ, J9s an Kx in his value range. You barely block anything of that.

James Hudson I made a quick sim with mostly one size per street, for the purpose of showing approximately where the calling thresholds are vs turn & river overbets. I didn't save it, but if I recall correctly the IP player wants to bet a lot on the flop so probably the best strategy is to bet range there, and I used a neutral size (66% or so). I also assumed a microstakes CC from SB wich is kinda wide (about 20% of hands with a lowish 10%-12% 3-bet).

Also the OOP player doesn't like overbetting for that amounts at all, specially on the river. I allowed two sizes for him on the river and almost never went for the overbet shove. In the two sizes sim IP was mixing calling/folding with more hands like KJ, probably folding J9, I don't remember, but showing that trips/low straights are indifferent at best.

I re-run the sim forcing him to shove or check -because given that the line is taking like less than 1% I thought there would be some margin of error from the solver, and got the pure KJ or worse/J9 folds.

So take it with a grain of salt , the sim was.intended to follow OP's line and try to get a good grasp of bluffcatching range, a one-purpose sim because changing stuff and re-solving takes too much time with complex, complete simulations.