Hi Maybe,
Hard to say which way it will go. He could be speaking God's honest truth when he says he may learn to like living alone, or he could be using this as a manipulation tactic. After having lived alone for five years, I can honestly say it is easier (I'm not PTSD). For someone who is constantly on the verge, the benefits of being alone may prove to be greater especially when one does not have to consider someone else 24/7.
So the question for you is, do you want a part time partner, a relationship that seems more "friends with benefits", should he decide that being alone is the best thing for him? Or would it be better in that case to sever anything romantic, and have him involved only in the childrens' lives? Should you decide to remain together in the true sense, remember that it will always be a roller coaster, hopefully with the good outweighing the bad. That all takes work on both sides. I'd say right now, your peace is worth more than anything in the world, and it will also bring a sense of peace to your children. Dad needs to be involved however he can, but you need to provide stability for yourself and your kids above all. Take your time, before deciding to jump back in, if that is the way you want to go.