Back to the issue...
I'm no psychotherapist or anything like that, but has counseling been suggested to either/both of them? I personally don't put a lot of stock in it, but then again, I've never had counseling for anything.
If the heel is too much of a fuckstick to benefit by counseling, maybe your mom can take some solace from it. Hell, maybe she'd even get up the gumption to kick his lazy ass out the door, and begin anew!