What can I do if I co-signed on an engagement ring to someone?

I regrettably co-signed on an engagement ring after my fiance proposed to me, because he simply didn’t have the credit needed. The back story: Shortly after, he brutally abused me and beat me bloody, and badly damaged my SUV with a kayak paddle. We both ended up in jail, because he claimed I had stabbed him with a knife when he was hitting me, and that his abuse was self-defense. This was not true, although I was temporarily charged with aggravated assault, the charges were later dropped by the state. They found his injuries were self-inflicted. His charges however, were not been dropped. He had a severe problem with drinking and pain pill abuse. Currently he is in a trial diversion program (I wished not to testify) and must follow several new rules to keep himself out of trouble. He also received a DUI and a shoplifting charge during this time. Obviously, our engagement was broke off. Now more to the point, when I retrieved my possessions from his home some time after, I agreed to give him back the ring, so long as he resumed payments on it. We were supposed to sign a document to note this, but in all the commotion, I forgot. Now he has given the ring to a NEW fiancé. I am now continuously getting harassing calls from Jared Jewelers because he has not made any payments. I tried to write him about it kindly, and received a long drunken response late in the night, the gist of it being “You should obviously not worry about something so stupid as a ring payment. It just shows you for really nothing worth my time to reply to. In other words, leave me alone and accept what life is foe you now. I don't care about anything that involves a payment t to Jared. Let alone anything to do with you.” He is incapable of a civil discussion to come to any agreement, and I don’t know what to do. Small claims court? He doesn’t care about his credit, and would gladly take me down with him. After taking care of him financially for 4+ years, I just can’t bring myself to bail him.