She sounds awful, OP, quite unhinged. I think he needs to hear that he doesn't need to put up with this, that he is worth more, and that her behaviour is very wrong. And that the pattern of abuse is usually one of escalation.
DP was in a relationship that was very abusive - for 19 years! (He would have left sooner, but didn't want to leave his son with his ex, he eventually left when DSS was 17). She was financially, emotionally and physically abusive.
One night, when they were both pissed, she went into an abusive rant
and ended up throwing something at him. It cut an artery in his temple. Their lodger insisted on taking him to hospital, he'd never have gone of his own accord, and a friend and one of his siblings more or less staged an intervention.
I swear she'd have killed him if he'd stayed. I knew them both pretty well, and I had no idea this was going on - I thought they just had a volatile relationship, the way some couples do.
I hope he manages to end this relationship, the sooner the better.