Hi Allthattheywant
My heart goes out to you as you suffer through such torment. Whilst your torment of mental and now physical abuse is obvious based on what you say, your wife's torment is perhaps not so obvious.
I believe people will drink typically for 2 reasons, 1) they either like the taste and will have a few here and there or 2) they are using alcohol as a drug so as to change their mind to various degrees. When I say 'change their mind', what I mean is that they don't like the way their brain/mind is working without alcohol, a factor which can lead to addiction/dependency. Been there myself, some years ago.
After 20 years of being together, to say this is a tough call would be an understatement. Perhaps it is time to lay the cards on the table; tell her you're considering leaving. No one deserves to stay in an environment of ongoing abuse. Whilst your patience and compassion may have been exercised and strengthened through these upsetting times, there is not too much opportunity for evolution in such a situation, especially if it's not going to change. It becomes more about destruction than anything else.
An unusual suggestion but have you ever considered recording your wife's behaviour on your phone, including her having passed out on the floor? Of course, you wouldn't be sharing it with anyone other than her. Showing her this video, when she's sober, is one way of getting her to literally face how serious and destructive the drinking has become. If she was to say 'I don't want to look at it!' this would be an opportunity to say 'I want you to take responsibility and face the impact of your drinking, on both you and me. I want you to face what I have been facing for the past several years'. Some form of intervention/disruption regarding the addiction may have an impact. Whether it involves something like the recording or a group of friends or family members coming together, it's basically about disrupting her way of thinking ('Alcohol's not a problem in my life'). If she finally takes responsibility, supporting her through a constructive course of action may strengthen the relationship. If she does not, taking responsibility for yourself (leaving) will at least allow you to evolve.
You mention that if you leave your wife she will most probably die.
Given that she drinks so heavily to the point of often passing out, if
you stay and nothing changes the outcome
may eventually be the same.
Take care