Then again, they never did cohabitation. They dated and moved in together after their wedding. He admitted that if he knew she was like that, he never would've married her. He got used to her intense mood swings, her thoughts that everyone is against her, her believe she can read people's minds and impulses (ex: spending all the money for the sake of it) by now and won't divorce her. At this point he continues staying out of compassion for her mainly but he's not the young woman he once loved.
If they were just boyfriend and girlfriend, you can break up at anytime. However, how bad is it once you already have kids and are married to someone with BPD?