Fold on the turn. Don't think he's ever folding after this bet and your hand is way behind. I would most likely fold on the flop even though it might seem weak. If he's aggressive he will barrel most turns and there isn't much you can do about it

Many ppl  play sets on str8 board just like that of what ive noticed, and you cant do anything abt it because he wont fold, even if its an overpair plus FLDR, so IMO its wrong to call flop xr even if you know he hasnt got a str8,because he is showing willingness to not letitgo anyway, and only thing you can hit is clean 3 outs which is eeew, but if you think you coulda fold him out you could have tried rereraise on spot eventually, tho how ppl go in love with some hands i dont think this 1 will let it go

fold pre.  calling a three bet OOP with 8664 is speculative at best.  as played fold turn.  your spade and straight draws may not be any good even if your draws come in.  and if you miss your hand has no SD value to speak of.  

fold on flop, no reason to call xr 

"Now he double barrels, bluffs with some diamond draw + high pair. That's what I see here.What are the chances he plays set like this?"

Don't forget the most important hand, which is the nut straight. You can fold the flop. Blockers are good for bluffing, but not so much when your opponent takes the lead away from you. Furthermore, the flush draw on board really hurts your equity. 

Thanks for your responses. I just hated this spot cause he was most likely bluffing, I had 0,00 fold equity as I play vs maniac, and rare times he holds either set either nuts here. My equity isn't great neither.

Regards to all.

Best possible scenario for you,  try keep in mind even if it was a win is incorrect play ;-) even pair 7 win over you