Why don't you think he's chasing? I put him on a diamond draw, ace worse kicker, maybe AK or something kooky like Q8 or a slow-played 88. If he's on the diamond draw or has AJ/AT (the most likely hands, imo) the push is terrible b/c you're getting called by better hands and folding worse hands. If he has something weird like AK/Q8/88, then the push is better b/c he might fold a better hand when the flush hits. BUT, given he's been calling and not raising, I'd assume he's a station and isn't folding anything but AJ or worse here.

I like c/c river I think, maaaybe c/f to a push, but he has ~1/2 pot behind, so probably not.