The ideal first step is to contact your ex to find a solution:
(a) If more than one person is on the 1095-A, have him amend his tax return to claim 100% of the 1095-A. He would then give you a copy of the 1095-A, and you would enter the information on your amended tax return and claim 0%.
(b) If your son is the only person on the 1095-A, have your ex pay you the amount that you need to pay on your tax return.
If your ex unwilling to do that, or if contact with your ex is not a good idea, then unfortunately your only option is to pay the IRS what they are requesting and to contact your divorce lawyer. Sorry for the bad news.
