3rd Barrel Or is this too thin?

Aside from slow-played monsters, or the rivered 2-pair, the only hands that make sense for Villain are Kx and spades. Even though we really don't have enough left to properly bet-fold this river, I'd still bet $100 to try to get a call from Kx.

i go smaller on flop and bigger on turn 3 ways.

i just check river, i dont think worse calls you unless you go really small. and two pair sometimes checks behind saving you a bet.

once you check id fold to any big bet.

I would probably check the flop to let MP stab at it with all his Kx and his draws. Depending on the sizing he takes, we're either check-calling or check-raising.

If we're going to c-bet, I think I'd go larger with the two spades on board, like $45 or full pot. I'm probably over-betting the brick turn.

If you have a read that an opponent likes to bet when action checks to him, then maybe check the river. But absent any reads, I probably just barrel here. No need to go huge. I'd probably just bet $100 to target his Kx holdings.