we could be way ahead, way behind, or barely ahead. with villain leading like this, it's much more likely that the 'way ahead' option is out the window.

to be honest, this looks like either or more than anything else, for the following reasons:
A set raises flop more frequently than call. A flush is usually way ahead and would not show massive strength on turn after a scary card on this street. A straight, is the most vulnerable hand in this spot for villain because you could have any spade... hence the large bet.

This line just screams protection.

I wish I had this much time to think through every turn decision because I'm leaning towards fold but would be reluctant during play.