I'm so sorry your dad is having a tough time right now. And I understand about being "Daddy's girl". It's very hard to see your parents suffering and to see your daddy cry is earth shattering!
Sound like you have been very blessed to live to close to your folks. Mom's and daughters often have these love/hate things goin' on. Don't worry too much about it. Just try to be sensitive right now to her feelings too. This is when you can be a great daughter to her.
It's good that your dad trusts in God. That will help him through this time. God has plans for all of His own and He hears the prayers of His children. I'll send up some on behalf of your dad and some for you and your mom too.