There is nothing wrong with choosing, as I did, not to watch someone die. I'm just pointing this out because earlier you mentioned that you have no choice but to witness this process until the end. There is always more than one option.
I know you're hoping that your brother will somehow be able to overcome his physical challenges, but there is a reason that the last stage of alcoholism is called the end stage. For me, it got to the point where I didn't need a doctor to confirm what I was witnessing with my own eyes.
I think your brother has chosen his path. We're here to help and support you. I have walked in your shoes and watched someone I loved succumb to alcoholism. The pain is excruciating. I don't have any words of wisdom to share, only a deep understanding of the fear and pain you're experiencing.