I too am sorry for the situation that you are going through.
My alcoholic father passed away last year at the age 71 after being sick for approximately two years. During difficult times, I found comfort in the serenity prayer. His illness and what became of his life was definitely something that I could not change.
I would also pray a lot and picture myself placing my father's care into the hands of his higher power.
Wishing you strength to make it through this difficult time.
db