Well I do not think that I "should" have to pay him back but honestly I was open to the idea. He went on about his drug problems, how he lost his job, gambled everything away (fiat too) and was now homeless. I felt sorry for the guy but I do not think there is an obligation for me to give him anything I have.
I lost more money trying to do what he demanded by trying to fill his contract. I lost almost everything at one point when I had to pay back everything I owed. I'm one of the very few who did.
Now the only reason why I have BTC today is because I borrowed from family and friends and went all in again. I did well with AM stock and LTC.
Now should OP get a part of that? Well, I asked him why he thought he should and his response was a year later "Hello Scammer, should I report you to the FBI/SEC"
Honestly if he is going to be like that fuck him.
Also keep in mind he did not invest BTC into this. He invested GLBSE bonds that had a questionable value. I was trying to be nice and help him out at the time. Something I wish I never did.
Anyway had he been reasonable and polite I would have come to an agreement with him and done something in fiat in the range that would have made him close to even, but only cuz I took more personal risk after the fact and won. Not because he is owed it.