Webr3, dont you understand?

Its very clear that he owes you. As clear as that is the fact the he can pay you "WHENEVER HE WANTS", as long as ther is not a path for you to redeem your IOU.
So better than pushing him is to beg him to give you Bitstamp BTC.

If he has the BTC, then why make you suffer? I agree that he should try to pay you because you helped him to prove his point, as a fellow.
But he cant be tagged as a scammer.