Dung, his mum knows because I told her. I wanted her to be aware as I knew he'd cover it up. I wanted to spare her the shock, so while she wrongly thinks she can influence things, at least she knows what's happening and when whatever happens happens, she's had some warning.
Amibeing...unfortunately it's very hard to get legal aid in these circumstances. It's not the sort of thing you call the police over so unless he's been charged with something, i.e. usually physical abuse, hard to prove. Unfair but that's the way it is.