I think we often romanticize the fantasy of a relationship rather than the actuality of it. You have said you don't miss him and you don't' want him back - I think perhaps you are angry that he seemingly doesn't have the repercussions that you have had. Certainly the marriage wasn't as painful for him as he was the cause of the problem. He has blamed you for leaving it, and not he is skippy in love with someone else and wishes the best for you.
Please remember the insanity of what it was like to be with this man, not the fantasy of wishing he would sober up and you would live happily ever after.
Having been down this road with him before you know that no major life changes are advised in the first year of sobriety. I wouldn't say that's applicable to your choice to divorce, but is applicable to his choice to enter into a new relationship with someone else also attempting to recover. That is strongly frowned upon, and I personally doubt it will last. Nonetheless, while he is all happy and "in love" (term used loosely) I would RUN down to that dystopian court and file those papers with glee. It may make your divorce amicable and easy.
One should not look a gift horse in the mouth. I am sorry its hurt you - but tis best to end this all before they implode and he decides he wants you back (which most likely will happen).