How can you deal with a parent passing away?

I have complained about my dad in the past, but the truth of the matter is I can't imagine life without him. He is my best friend and the one person I go to for guidance. This past year we both got covid, and he has the covid tongue (his taste buds are gone). He has muscular dystrophy, more specifically pompe disease, and he has lost so much weight. He told me today that he thinks this might be the beginning of the end, and I just broke down and cried. I told him, "How am I going to live without you?" I don't think my mom and siblings understand how close me and my dad are. My sister acts like I don't do anything to help out when really I cook for my parents, I help clean, I help my dad with everyday tasks, and I make good grades at University and I try to keep a positive look on our situation because it's the only thing keeping me sane. My mom is so angry now, every day I have to pray she's not gonna lose it on my dad, and I get it; she doesn't want to take care of him because she can't handle it and she has her own bullshit to deal with. Truth is I don't want to lose him, he is my everything, and I don't know how to handle life with him gone.