Where do you come by this absurd notion that the divorce decree "protects the co-owned property" against any of your ex-husband's attaching judgment creditors?
Apparently you are oblivious of the meaning of "due process of law" as if a family court would have the ability to preemptively deprive his judgment creditors - present or future - of their right to levy against his undivided one half interest in the home. Trying selling that "theory" in an attempt to abort an IRS lien!
Secondly you are dreaming if you think that "when and if needed" the court will allow you to reopen the divorce case and order your ex "to agree to sell" his undivided one half interest in the home. You can no more compel him to sell his vested interest than he could force you to sell your vested ownership.

