Wellcome Tantalus,
(your nick certainly sounds appropriate). So sorry you're going through this.
I agree with others who say you're wife is grown up who should be responsible for her own life, but I think it is obvious at this point of her alcoholims she's uncapable to think or act rationally or responisibly. Also IMO things will not ger better unless she gets treatment and during that time maybe does enough work on herself to decide she wants to recover. Also, lately I think the alcoholism is always only a symptom of some deeper underlying problems in personality. My opininon is she would have to work on these issues first. But you know all this.
I think if you still want to keep trying to do something for her, you can try having her committed into psycic ward, I don't think that should be a problem with all the suicide threats. That's something I'd do.
Actually that is something I did. I'll tell you my story. Six months ago my RAH, stil active in drinking, started looking very bad, losing weight, having all kinds of crazy bahaviours, and at some point I realized he was possibly dying. he kept refusing to go to the doc's, so eventually I asked him to move out, so he did. I knew at the time he was unable to think straight, to make any decisions, but I just simply couldn't take it any more. I was terrified of the idea of him dying with kids being present. But I decided to just to try to do another thing before I let him go for good. I phoned his mum, and made a huge fuss over him going to die, and that they have to take him to hospital, so after resenting me they decided they don't want to take chance that just maybe I'm right, so his brother literaly dragged him to hospital.
My RAH was diagnozed with end stage liver disease, and told he is not likely to survive. 3rd day in the hospital he suffered DT, halucinated he's being chased by someone and run away from the hospital. The morning after friends found him wondering the streets, all bruised, his clothes torn, barefoot and wet. I committed him to psyhiatric ward, and they took care of him but only overnight, as they were worried they can't treat his liver problems properly, and were afraid he might die there, so they shipped him back to the initial hospital. Of course they were reluctant to have him back there for the fear of more episodes. I insisted they have him strapped to his bed. He was on strong tranquillisers until he's liver started working a bit better, so his brain started clarning from the toxins. After one month in the hospital, and since he was recovering well (I guess mainly thanks to the fact he's only 38) they send him to home rest. The same day I took him back to the shrink, who's been working with him ever since. That was a month and a half ago. Only recently I can see he's able to think straight, he can make rational decisions, and the more he's able to do that, the more I'm stepping back and letting him take charge of his life. As before he was simply unable to do that. I don't know what is going to happen, if he's going to stay true to his recovery, I can see he has his heart and mind in the right place for today, and to me that is good enough. If that is to change than I'm afraid I'll have to let him go his own way. This is as much as I can do.
My point is this, and I'm only saying this bacause you've asked for advice: you should do something: either have her committed and maybe give her support through it, or just leave her and remove yourself from this situation, whatever feels right in your heart, but please remember, and this is only my opinion, things will not get better by itself, as I'm afraid it sounds to me she's passed that point where she can help herself.
Also, I'd like to say, please take care of yourself, and work on yourself. Through all this ordeal in my life in the passed 6 months I have learned so much, most importantly how to be happy regardless of other people.
I wish you well
PS And all that guilt is not helping you: you did the best you could, that's is as much as any of us can do. Forgive yourself for everything you feel you did wrong, you're only human.
Take care