No legal advice here, just my condolences.
One of my daughters was in an exceedingly difficult marriage, and tried very hard for 24 years to make it work. Her husband at the time was a liar, a thief, a narcissist, and a druggie, with a bunch of very difficult behavior problems, being manipulative, domineering, and controlling.
My point for all that is that your brother can be honorably released from his marital obligations if he has done all that is possible, no progress seems possible, and the present situation is personally destructive. It's a marriage, not a suicide pact.
FWIW, my daughter got a protective order, which her husband violated with impunity. So the courts issued a second order, tightening the restraints and upping the penalties. He violated that one too, liberally. So the court issued a third order which permanently barred him from ever being present in their marital home. When the divorce judge saw that, he awarded the home to my daughter.
Oh, and my daughter just remarried, to a terrific guy. However bleak it is now, better times are ahead.
