quit claim

i bought a house in 2006, and my ex-boyfriend's family gave me a financial gift to put down on the house. a few months afterwards, they wanted me to sign a quit claim deed that actually says that me and my ex would own the house jointly as husband and wife forever. it was not filed. they said, "in case i died", i needed to sign it so they would not lose that money to the bank." the loan/mortgage is entirely in my name. well, we broke up now. the house is underwater (by a lot, probably $100,000). my ex says that he will not ever give up the quit claim and that is plan is to let me 'save my credit' by making the mortgage payments. then, when the market goes back up, he plans to take the house when he can sell it at a profit. i am not very interested in making payments on a house that he will suddenly take from me 5? 10? 15? years down the line. so, i was actually considering just allowing the house to go into forclosure and using my mortgage money to then work on fixing whatever consequence that will bring me. i am just wondering if i have any other option?