I just want to second what others have said about you doing well and being strong.
There is another thing I'd like to add, I know all too well those thoughts about burrying him before he gets sober.
I have been burrying my STBXAH for few years now, anticipating his death, as he had so many health problems, almost dieing from liver cirrhosis being one of them, but guess what? He is still alive. So many times I was absolutely sure he will not last more than few days, but he did.
My point is: there is no way you can know how much longer he'll live, so if you don't think about him dieing you're just sparing yourself some additional pain.
Nowdays my A is in rehab. There is no way anyone can tell whether he'll make it this time or not.
Sometimes I joke with my friends that after all those agonies I had over him dieing he might acctually outlive me. Like he can get well, and I could get some nasty disease from all the stress that was ruling my life for years.
I know how hard it is to part ways with person you love, but sometimes that is the most loving act one can do. You're letting him own his life, it is all up to him. You can only own your own. So be gentle on yourself.
No one knows what the future might bring, the way I see it your only job is to make sure you're there once the future happens.
Take care, you're doing well... One step at the time
HUGS