I appreciate the suggestions to let my husband handle this. A big part of my problem is I handle the weekly phone calls, which doesn't sound like much, but if you're trying to schedule with someone with severe anxiety, no sense of time, and a loose grip on reality it's a chore. Sometimes she calls in the middle of the night on other days crying and asking why we haven't called yet. If I could turn his relationship with his mother over to him that would help.
Why can't he establish appropriate boundaries for the calls? The time for the call is Sunday at X o'clock. Oh, that doesn't work? Sorry, mom, we'll have to wait till next week then. If she calls in the middle of the night don't pick up, she can leave a message if it is important.