He cheated... the wedding is off..do I return the ring?

I found out that my fiancee had cheated on me and got the girl pregnant. I left him!!! But now he wants his $6,000 engagement ring back. I don't want to give it back to him yet, until he helps repays my parents for the $20,000 wedding that isn't going to happen in 2 weeks. I was going to sell the ring and give the money to my parents. What should I do?