Tbh i think your smoked here way to often to justify a river call as its fairly unlikely he fires 3 barrels with anything worse, even a missed flush draw with his passive tendencies. Its also unlikely he has a flush draw as you have the ace of spades plus having the k or q high f draw would likely result in him checking thro due to him pairing up. So his most likely holdings here are kq,44,88 and at a stretch k8. With all of these beating you river is a fold for me. I also noticed his weird less than half pot turn bet which seems like hes really trying to not scare you away and his river bet looks like a value bet if ever i saw one.