he told me that it was highly unlikely that mediation with an addict will work.
That would be my primary instinct, too. If you do decide to give it a shot, however -- read the fine print thoroughly. In some states, if you come to an agreement through mediation and sign it,
you waive your right to take it to court. That's a huge big whopping WTF in my analysis of the judicial system, and one that makes it more likely that a manipulative addict would want mediation. Because if they can manipulate you into accepting something ridiculous, you've got no recourse later.