Hi there, full sympathy for your situation, it's hard to be rejected like that especially if you're the one who tried to invest in a relationship with someone who didn't care.

I wouldn't spend too much time trying to understand. He's either depressed or an a-hole and that's as much explanation as you need for the moment.

I recently read a book called "On Your Own Again". Is specifically about the stages of grief after a breakup. The most insightful thing for me was that the author mentioned that there's a specific grief about the loss of the relationship which shouldn't be confused with the loss of the person.

Your kids seem to be giving you some pretty good cues that this is making them happy to be away from him. Grieve and go through your emotions like you need to and move on.