Welcome to SR Broken. I'm so sorry for all that you've gone through and for the pain that you continue to have.
Have you considered going to Al-Anon? There will be many people there who have had similar experiences.
Alcoholism affects the whole family and can have devastating consequences. For your ex-husband, his need to drink came before everything else. Only he can change that, there would have been nothing about you that could have done it for you.
I really hope that in time you will be able to rebuild your life for you and your son and find your peace.