Sounds like its time to dom up. If she wants her men to be dominant then drop the Mr. Nice respectful thing and put your foot down. That's how I would play it anyway. I get really concerned when women go to doms and lose track of their responsibility because they are too high on the BDSM thing. It can be a drug for both parties and these two sound like they are in it bad. If I were in your shoes I would not date anyone and concentrate on getting your wife back.
She sounds like a whiney child to me and they sometimes need to be put over the knee and spanked (mistress talking here
). Seriously, I wonder if she would respond to a little assertiveness on your part. It might jolt her out of it.
As for the dom, I think he could babysit while you sort this out. Time to step up and be a real dom, one that has integrity and considers everyone involved. He's slacking on his responsibility by being selfish.
Maybe once they come down from this and get back to reality, they could take two weeks holiday together; one for him to beat her just as she likes and one to heal from it (emotionally, physically and to come back to reality). I wonder if you suggest this as an option (shows you are giving) there would be some movement towards thinking of her responsibilities again.