Hi Name,
What I would do is send a group email, or message each friend individually. Write something like, “Hey guys, I want to apologize for being really s$$tty to everyone this past month. I found out my dad has cancer. I know that’s not an excuse. My reaction has surprised even myself. I’m not good at this, but I will be taking care of Dad for a while if you don’t hear from me.”
It sounds like you’re young and haven’t experienced any serious health issues with a loved one before. It IS a shock, and an element of unreality does come into play. Be there with and for your dad. Talk to the doctors with him and take notes. When you do research, skim over the scary statistics and write down what you and he CAN do and SHOULD take to beat this. Help him find help at home if it’s really bad.
Blessings,
Inky