Hello and thank you for allowing me to address your legal question.
Unfortunately, I do not believe that the signed document will have any legal enforceability, unless you gave your ex something in return for releasing your obligation. In other words, a contract is not formed unless both parties promise to give something. A one-sided promise is not a contract, and therefore, is not enforceable.
For example, if you promise to give me $10 for cutting your lawn, and I promise to cut your lawn for $10, then we have a contract. On the other hand, if you promise to give me $10, but I don’t promise anything in return, then there is no contract and I cannot legally force you to give me $10. Does that make sense?
I know that’s not what you wanted to read, but I hope my answer was helpful. If so, then please remember to ACCEPT my post as that is the only way I will receive credit and compensation for my answer. Thank you and good luck!
DISCLAIMER: Please understand that the complexities of most legal problems cannot be sufficiently addressed in this setting. Accordingly, my post is intended as general information only, and should neither be construed as specific legal advice, nor as an adequate substitute for the retention of legal counsel.