I think you are absolutely right; in fact, I think part of his reason for leaving is because he knew he was heading off the deep-end addiction-wise. He may have left to have the mother of all benders.
I have started going to Al-Anon - I should have gone a long time ago. H was in active recovery in NA a few years ago, but after two years of being completely clean, felt it would be ok to have a few beers again and it progressed from there. A lot of my current resentments started with those 'few beers', because I knew we would eventually end up here.
Me: 40 H:42 M 13 yrs, T 15yrs SD19, D18, SS15 BD: 3/4/17 - ILYBNILWY He moved out: 4/3/17