His obligation is to try to work on it. If he can’t, he should leave. The children aren’t helped by living in an envirement where 2 people are fighting or where one person (the “crazy” wife) snipes at the other and the other (the “tzadik” husband) is a doormat. If he thinks she will run away with the kids, he could go to court about it.
Most of all, I think he should go to a rav who HAS EXPERIENCE with these things and make some decisions, not just listen to the advice of total strangers.