Preflop seems fine, I have no problem folding or raising there (but no limping).

Flop obvious.

Turn I think calling is probably what I would do. However, I'm surprised nobody advocated raising. Clearly, his line is weird. The purpose of his turn bet is likely to either be a moderate hand (perhaps one with outs, i.e. a pair+picked up flush draw) hoping you fold, or a two-pair-to-monster strength hand looking to milk you or just make sure it isn't checked through. Air is, of course, also always possible with weird lines.

Of all those, I think a pair plus some sort of draw is the most likely. Any pair with a 9 now has an OESD, any pair with two diamonds has a pair and flush draw. So, if you jack it up to say $300, you put a good price on those hands and get a check behind on the river. You didn't specify a read, so I'm assuming it's a standardish 5-10 player, meaning a fold is in order if he pushes. If he's got the monster, you lose the same as calling down when you fold to the push.

The disadvantages of that line is when he pushes as a semi-bluff, or when he folds with air when he would have fired another barrel. However, I think in this situation the pros outweigh those cons. Thoughts?

ANYWAY, as it WAS played, I just call the river as well. Only possible hand I see you missing value from with a river raise is a K7-ish hand, that also hit two pair on the river, or perhaps one of those smaller two pairs. I think those types of hands are far less likely than one pair hands or monsters.