Donate it, drive over and leave it on his family's porch or mail it back. I wouldn't go to too much effort or expense. He's kinda playing both ends against the middle, isn't he, by saying both he 'didn't leave anything behind' and that you're 'holding things hostage' so he has to deal with you? What does the last text say? "I didn't leave anything there"? It's winter here. If there was warm clothing I'd give it to the first homeless person I saw. Done.
I have had fake friends who borrowed money and never paid it back. They are no longer friends. As for his family: well, blood is thicker than water and chances are they're going to believe his story that you're an awful human being, rather than look at the truth that a little boy who can't hold a job or finance his own apartment has a problem.
In my 60 years of observing humans, breakups work better if people don't try to maintain a friendship. One person generally feels rejected, and any contact with the person moving on is interpreted as a willingness to renew the relationship. It ends up being more confusing and hurtful than just walking away. YMMV.