Hmmm, I know your probally very very angry by what your father did you to and you have every right to be, however after just finishing cancer treatments, it really does change your prospective on things..
Just ask yourself if there is anything you would like to say to your
dad incase something happens? Im sure your father is very very scared
right now, cancer is a very scary word and when you hear it and its about you
you think of death!! Each day turns into am I going to beat this, am I going to die... well at least it did for me!!
Remember if something does happen to your father you may regret it forever.
You dont have to " forgive" him for what he did, but perhaps it would be
nice to be there for him and your mom should something terrible happen.
None of us on here know the relationship between you and your parents so its hard to offer advise , however having seen so many people going through cancer treatments you would even have compassion for a complete stranger..
I hope things work out for your family , good luck