[Minnie]

Can us non-lawyers/not-legal-experts chime in?

I don't know the legalities of this (as in, whether this could net him custody), but if he thinks anything is happening and he is finding evidence, is he documenting/screencapping this stuff? Because that's one of the first things I would do. And, if I were the non-custodial parent, I would be doing my absolute level best to keep *my* nose as clean as possible, so that if they go for custody, it's the custodial parent that comes out looking like dog crap on the bottom of a shoe, particularly if they're making concerted efforts to alienate the child from the non-custodial parent.

I'm sorry this is happening to your friend.