I think you push here. The number of times he does this with the flush or 8x outweigh greatly the times he has a set of 9s or 89. Especially considering the info that you've been making some great calldowns on him and he may be a bit perturbed by you (He could just be making a play with a slowplayed big pair? Is that possible?). If he has the nuts, you just have to pay it off IMO. I doubt however that'd he make this play with 8x with the flush on board (though I could see him doing this with 8Ac). You could call and push the river. Either way I don't think you can get away from this. These stakes are way above mine, but I don't think at any limits you can lay this down? Am I way off base here?

I take it you pushed and he had top set.
Cool hand though.