AT84ss

No need to bet the turn and river so big, half pot is okay. Decision fold or call river depends on reads and stats, normally a set would raise the flop and the nutstraight would raise the turn. But you never know with those recs. :-)

I would fold if unknown opponent. His line doesnt really make sense, which means that they usually have it.

Now you have a read from him that he goes nuts with bluffing with almost the worst possible hand (busted nfd) against uncapped 3 barreling range

open looks okay. PPT ranks this as 33rd percentile hand.

check back the flop. also I don't care for this smallish sizing on such a dynamic board. it's not generally a good idea to pure bluff with cards to come. true, you do have a gutshot, but it's not a great idea to semi bluff in position anyway, since you can just check and see if you hit. you should semi bluff out of position against a tough opponent.

gin turn is an spot to keep betting.

maybe river could be a check back. it is tempting to go for value against Kx of spades or hearts, assuming this hand doesn't just try to play for stacks on the flop, but for the most part villain is going to have either a draw that missed, so won't call, or a hand that boated up. anyway given that you did bet the river you should fold to the raise. very unlikely villain is bluffing or doing this with three of a kind for value.