Prayers for you and your family!
My mom passed away in a nursing care facility several years ago, at the age of 95. She had Alzheimer's as well, and I learned a lot about the complexity of it... a strange and difficult condition that causes anxiety and paranoia. I guess when you live in one world and much of the time, your parent lives in another, it's not easy to communicate. Imagine being told that you are going into a beautiful garden but all you see is being led into a raging fire.
The saddest days for me was when Mom was lucid and realized what her life had come to. She would cry and feel miserable, and then slip back into the Alzheimer's world.
I pray for peace for your father and for you!