1655 to call, Villain's 1655 + 900 in dead money.

That 1.55:1

2:1 to make a Flush

Also have outs to a set, two pair or runner runner straight.

Pair could even be good if Villain is on a draw with overcards.

I don't think Villain flopped a set, as a middle pair would've raised and been happy to steal the blinds. Same for a hand like A9.

I'm guessing he slowplayed a big pair and freaked when he saw all the draws on the flop or he's on a draw himself and is semi-bluffing?

My gut instince was to fold until I started adding stuff up. With your chiplead, I say Call. The pot odds are good enough to hitting an out or finding out that he's stealing with crap.