Effective stacks are actually only 400bb deep but I get the point. I'm not sure if you're being sarcastic or not but I do think its an interesting hand and am keen to discuss it with you. I am still learning at poker, so by no means do I consider anything I'm saying to be objectively correct. Btw, the hand reminds me a little of this hand:
, huge hands, wired flop and tough decisions.
I haven't ever played 500bb deep except in tournaments, but I would think that regardless of how deep stacked you are, it is not standard to put in 4/5 of your stack and then fold. But then again, that could be what makes it a sick fold. I guess you're still left with ~90bb which is by no means insignificant, but at the same time you've lost 400bb. But generally don't the same rules apply postflop, its more about the pot size and relative stack size than how deep you are? I know 90bb is still a lot, but there's a 680bb pot there, and AK is the only hand that has you beat.
Does the concept of pot committal not apply when you are over a certain amount of bb deep? I would think that it applies no matter how deep you are, but I am open to the fact that I might be wrong, I don't know for sure.
Let's just say that he did have AK. There are so many reasons not to fold, that I guess by that you can say it is a really sick fold, he did have the better hand, so in that respect well done! 
The only dilemma though, is that supposedly as poker players we are not supposed to be results orientated and knowing that he had AK makes this results orientated. Although I am not sure if I fully agree with always being results orientated. I think sometimes you can be. It is quite a weird thing, to make the wrong decision in one isolated event because it is the right decision in the long run. Because I feel like here you got one of those "gut feelings" he had AK where you're just 100% sure villain has x hand, and you're right and you make the correct move for that isolated event even though its wrong overall, I know exactly what that's like, its a rare thing but it happens, and then is it ok to be results orientated? Who can say?
I guess the main question I have with this hand is the flop bet, it seems like it has no particular purpose. Are you expecting him to call this bet with worse hands than yours? And if you are, then surely you can't fold turn. It's a ~160bb bet too, shouldn't be made lightly. What was the reasoning behind making this bet? I think because the pot is 280bb at this stage and you've got ~250bb left, you really should to make the decision then and there if your hand is worth going all the way with. Not saying its an easy decision, because it isn't, but the flop is the time to make it IMO.
