Andy, I understand your frustration because I went through that with my mother regarding the chronic alcoholism. I am really in awe of the fact that you have stuck it out with your wife, as I just couldn't do it with my mother. There was too much anger and hurt. I cut off communication with her over 20 years prior to her death. I really could not believe that she lived so long, but she had to have sobered up at some point as she was living in a NH prior to being hospitalized. (I learned all this from her medical records, after her death.)
One thing my mother gave me was my own sobriety. I was traveling down the same road and when I realized I was becoming my mother, I joined AA. I was ready by that time, as drinking had ceased to be either fun or an escape.
I am sure there will be some lessons you will learn from all this. Nobody will think less of you for any thoughts you may have. They are normal.
You deserve to be happy. Please remember that.
I would like to suggest that Hospice be called in. They can be a great help to you, offering information and respite care, making sure that your wife is kept comfortable, etc. You can call them for info, but I believe a treating physician has to make the referral or confirm that she is end-stage.
Hugs,
Connie