Your post here is both inspiring and touching. Moving forward in your life is good, and I am so happy you have found the peace you and your children need.
It's okay to feel sad for your ex, his life is sad but he made his choices and is paying the consequence. You and your children do not have to pay too. You've paid enough.
I think you are wise not exposing your children to prison...and to see their father locked up there.
Keep moving forward in your new beginnings, and I have a feeling that the past will take care of itself.
Hugs