There is an old expression, "Don't look back, you're not going there". I think the "new beginnings" can only begin when we have made peace with the past and then there is no purpose in checking behind us when what is ahead of us is a fresh start.
It was what it was, and in your case, he hasn't changed and may not for quite some time, or if he is like my son he will continue in the revolving door of addiction/recovery/relapse...until there IS no recovery anymore.
I know it must hurt working through this and letting go of "what might have been" and I am glad you have support here and at your meetings to help you work through this in a healthy way.
Hug