You should agree to release the lien upon the close of escrow. That is, the lien should be released upon receipt of funds from escrow. Whether to accept all or a portion of the amount due is up to you.
If I understand you correctly, your ex-husband got title to the house in your divorce decree, but the court awarded you an $80k judgment lien against the house for money you invested into the house (separate, non-community property). Now, your husband is facing foreclosure and is selling the house. They cannot deliver clear title to the new buyer without the release of your judgment lien. However, it sounds like they cannot satisfy the judgment in full from the sale proceeds. What you need to do is to negotiate as much $ as you can from him (without killing their sale) in exchange for a "partial release" of the judgment. I can handle this for you. I handle these all the time.
You might ask that someone, such as the agent, post a bond for the amount. Or the agent can give you a lien on some other property. Or, you can become a party to the escrow, and deliver your lien release to the licensed escrow company on condition that the document not be recorded until you receive you money, within a certain time frame. I think that you should consult a real estate attorney to review the specifics of your situation and the relevant documents.