BTN vs FISH

My doubts here are:
Why are you not full stacked?
why did you cold called? I'd like to see your reasoning process here!

This is 888? If so on nl2 tables are 50BB deep.
With such stack we may call instead of 3b.

Preflop I'm fine with the call. On the flop, it's probably ok to call here. We have position with top pair good kicker, and a redraw to 2nd nut flush if a spade comes on the turn. He's making it pot size though, and he wasn't the preflop aggressor, so I'm sure he has something good here everytime.

On the turn I like the check back. Assuming he didn't donk the flop with air, we only beat 6x, worst kings and his flush draws now. Of these, he probably calling only the K. If he's got us beat, of course he's going no where and we have very low equity left.

On the river, I'd definitely check back for the same reasons as the turn, it doesn't seem like there much value to grab with a bet.

I would probably play the same way. River raises are usually very strong though. But you get a good price.