The OP makes it sound as if the husband has nothing to do with his family. If that’s truly the case, then nothing will be gained by staying in the marriage, they have nothing to do with him anyhow. If the parents are openly unhappy with each other (which sounds like the case here), the kids will be better off when the parents are seperated. Better to be with one happy one than with two unhappy ones.
What this guy needs is a good therapist, one that will teach him to start acting like a leader, like a parent, like the head of a household.
Trust me, I was in the exact same situation & therapy taught me leadership skills and I took control of the situation and now it’s all behind us. In fact, now, my wife respects me even more than ever because I took control, I stood firm by my decisions, and I righted a sinking ship. (And my kids adore me.)
You just need perseverance and patience. Nothing happens overnight. Patience, patience, patience.
Oh, did I mention another important thing that you need? Patience. Patience, patience, and more patience. And then some.