Nice work. As soon as I realized there were two conflicting scam accusations I figured the blockchain could shed some light on the truth.
Should I send the difference back or punish this little scammer for what he did? I cannot be the first victim, nor the last one. I think I'll send 50 USD to khaled0111 and donate the rest to an animal shelter or something.
Stealing from a thief is still stealing. It's been proven that he stole from you, and now you've recovered that money. If there's a way to prove the remainder was also stolen, then it should be returned to it's rightful owners. Otherwise, no matter what noble cause on which you propose to spend the money makes it any less theft on your part.