I wish I had some words to help you.
My mom has Alzheimer's. Her side of the family had 15 children(Northern Maine French Catholics) so 17 total. My grandfather died from alz, he was diagnosed and we lost him quickly a few years later. Out of 15 children about 10 or 11 have it. I am not sure about the one who's don't have it since I am not living near them like I use to. I know the chance of my two sisters and I getting it very high, very, very high. That is something that scares the hell out of me so I been preparing my family early on.
Every time my sister back home brings up that the nursing home has called and I hear what happened, I wonder what in the hell are they doing there. It is hard that I am not near my mom, 27 hours away one way, so I depend on my sister near her and the home to take care of her.
I have set up my records for my family on what my thoughts and wishes are before hand. They know if anything happens like what you wrote and more I have planned it out. All they have to do is go to my large file cabinet in my office, first drawer, the very large purple folder which holds everything I could think of from a to z so they don't have to wonder what to do. I am trying to lessen what they need to worry about and have to do and to have to do anything blindly where I am concerned
My mom made her thoughts clear on what she wants when she gets to this point which is good due to a sister back home that well, I have a sister back home that lives near our mom
What you have to go through sucks, and is so incredibly hard. Even though we know my mom's wishes, to go through them will be hard.
I am rambling, I apologize. No words to help you, sorry, with this difficult time right now for you. But if you need to talk about it more or vent about it please don't hesitate, I am a good listener.