What a thing.
So.. do you have an Alanon sponsor? How does she feel about this new information?
Remembering that I am on the far side of the computer screen, I can tell you from my perspective, nothing has changed. He was an abusive ass to you, and the damage he did back then is still exactly as it was.
This new piece of information may change his future relationship toward you... but I know if it were ME, I would probably start trying to plan around that eventuality... which is my OLD behavior... and which leads to disappointment - and...whattyaknow... more resentments.
Whatever 4th step your ex has...will be with his sponsor. If he finally gets well enough to do the amends step... that will be a long way from now, and will be only what HE considers necessary. Heck, there is a real possibility it won't even include you. (not that you don't deserve an amends, but if he was using, his memory may just not remember things the same as you).
So now you know that instead of dealing with an intelligent, educated, "together" man... the damage you received was from a hurting, raging, crazy, using addict.
Does knowing that he was not "whole" help lower the expectations around how he should have treated you? Sometimes, lowered expectations help me ease the resentments I hold.
They tell me in program that holding resentments is like taking poison...and waiting for the other person to die.
I do wish you well... and hope you can make some of those Alanon calls over this. I think it would be worthwhile.
(((loving, gentle hugs)))