This may be way wrong, but I think I call. He's not totally pot committed, so if he misses the flop he's probably not pushing so....

He bets/pushes and I've missed the flop = I fold

He checks and I've missed the flop = I bet 250 into the pot. If he calls, he's pot committed, so he'll likely need something to call or reraise. If he plays back at me, I fold. If he calls I check/fold and I escape w/about 600 in chips. Not great, but enough to steal from other shorties.

He checks and I've hit the flop = bet 125. I'm hoping this will confuse and frustrate him. Calling would suck for him given his chip stack; folding would seem weak so maybe it will induce an all-in bluff.

He bets/pushes and I've hit the flop = Probably all-in.