This is not legal Advise.
I can't quite see where you are going with this one? If the account is stolen and you have proof, why not submit the proof to the police?
Why did pay pal give you a some money and what for?
If you bring debt collectors in on this right now, you will have to produce evidence of this New alleged name and address that owes you money, it will then be his word against yours.
I think you need to give out a few more details on this case before anyone can give you the right advice, like what country do you live in? What did pay pal say to you? did you accept the payment as final from pay pal?
you still have rights as a consumer, but some more details are required.
good luck.