Big Hugs Jackthe dog. It is hard when someone else swoops in to save them and they don't make the crash landing you'd hoped they would to shake themselve up and see things our way. I felt this too. If only, if only he would have finally hit that lower than low he would have done what he needed to do-gotten straight, gone to anger management, learned to be a good husband and a good dad. If only! But that is just it-we can't make them see things our way. We cannot help if they find a soft place to land and still don't change. We can only make ourselves see things our own way. We can only change us.
Why do you feel you need to tell his mom? I know I felt this too and now that I can step back because it has been over a year I would say for me it was to be vindicated in some way--which now I know makes no sense. I need to take care of me and shake off what xah and anyone he has "told all about me"--any of the stuff they think and say about me. I need to shake it off. I know who I am. They do not. It is not easy though when you are already in so much pain.
Surround yourself with those who support you. Take care of you and your son. Don't worry about him. His transition is his business and your transition is yours. What are you going to do for you to make the transition easier for you? Set your sights on your future and the future of your son. Those are the things you can do.
Another fine quote by my sister--says it to me all the time. "Woulda, coulda, shoulda will not get you to where you want to go now." Be gentle with yourself. I am sorry you are hurting so much.:ghug3