Do you think his three and 1/2 months of progress were a test to see if you would really go thru with the divorce? He may have quit drinking, gotten a job, etc., just to show you, hey, I can do this..you don't have to divorce me.
But, you continued on your recovery path...and he chose to leave his.
If he was working on his recovery, for himself, this pity party of one wouldn't be happening. Don't get me wrong, it is sad, and tragic that he is in the position he is. But, he put himself in it....not you, his sisters or anyone else.
The saddest part of all of this, is that he doesn't care enough about himself to change.
Self-loathing is a paralyzing emotion.
Pray for him, and turn this, and him over to your higher power to take care of...