I can relate to your pain. I too was abandoned. The biggest lesson I learned was that I needed to get a life for myself. I had to stop thinking about how hurt I was and about the people who did it to me. Hasn't he wasted enough of your time already ? It's not going to be easy , but if you can come out on the other side of this you will be happier than ever. I say that because you got rid of a poison to yourself.
And don't care about how he's living now because he's probably not as well off as you think , and I'm not talking about money wise.
Good luck to you. Get what you can for yourself and son from him and
move forward, one step at a time.