Oh my......if he is drinking.....and taking antidepressants.....and taking anti-anxiety meds......it's no wonder that he's a mess right now. That's a bad combination all the way around. (Antidepressants and anti-anxiety meds are labeled specifically that alcohol should be avoided.)
You've done what you needed to do for you. That's great. Do you really want to get pulled back into the war zone again? I'm sure that he would love it if you did. It would take the monkey off his back and land it square on yours. What a relief that would be for him!
It is very possible that the mental health issues all stem from addiction. As you already know....you didn't cause it, you can't control it and you can't cure it. Your ex is a grown man and as such, should be able to take care of himself.
Take care of you.
gentle hugs