You’re doing all the most helpful, most loving things! You can rest in that. Speaking of rest, you might be on the verge of burnout. Helpers need boundaries. Perhaps I should add that to the list. Without your own boundaries, you’ll get caught up in the hell he’s putting her through, collateral damage of sorts. You might consider saying, “it hurts me to see you going through this. I get so afraid for you. I need to take care of myself, so I’m going to take a few days (or weeks or months, whatever you need) away from this situation so I can rest. I’ll be a better friend to you when I get back. I’ll call you when I’m ready to talk.”