marle, I too suspect that the build up of feelings is based on fear, and can totally understand that. The association between him and drugs is all too concrete and you've expressed many times that if it wasn't for him and his supply, she may well have stayed clean.
Situations like this are the kind where I only feel some relief when I go back to step 1. Powerless over xabf and his relationship with Megan. I think it is a reasonable boundary to not want him at your home and if it helps, to not want Megan to talk about her time with him. Praying for him or as Frankly said, that he will find his HP, sounds like the best way to "control" the situation. Many hugs and prayers for you all.