I can't help reading "we haven't been married long" and "the divorce was contentious" as "he was dating me before the divorce was final and possibly before the divorce was instigated." LW is really vague about the timeline.

The kids are in their twenties. They may not be the most functional adults according to LW, but they are adults; they are capable of making their own choices. And it's husband's job to manage that relationship, not LW's.