All I can share is what I did when mine refused to leave, I filed to get a personal protection order, then told my soon to be ex that he had 21 days to prove he was leaving or I would get a court date to get the actual order. I "promised" him that I would get as "creative" as I needed to get the order. He found a place to live and left.
Many addicts are paranoid about having to appear in court in front of a judge and will do anything to avoid it. I used that to my advantage.