Sorry to hear what your father is going through. I don't have any words of wisdom, but just wanted you to know I was thinking of you. I know you say your father doesn't want any help, but can you speak to a family member/friend about this so that they are aware of the situation? Maybe they could help you to support him as doing this alone must be very stressful for you.
I am sure others may have some other information/advice for you and if so, will post. Wishing you and your father all the best. Aileen x