So glad you were able to express your feelings today as this is all so hard for us to see and understand as those supporting the men we love. Fortunately every single person here will understand and relate to your anxiety and fear as we too have been there (I continue to "Go there" with each PSA looming now, even though my husband was reassurred that his treatment would result in a cure, and all is very well so far at 11 months post Sx). It is what we all hope and pray for. You will be OK, and will continue to be a major source of strength for your dad I'm sure.
Posting here for advice, and prayer is the way I managed this chilling fear too, and like you, I read ( and continued to read) far too much.... It does make it worse at some times, as others pointed out to me at the time, as we then may start anticipating things that may not happen at all. So I suggest, for your strength now, limit the reading about the radiation for the moment, and focus your healing prayers on your dad, and we will focus our healing prayers with you, and for you, in our own ways. Many people advised me that they too had taken a break from reading at certain times. Instead, our collective spirit will help now I hope. I pray that you will find the peace you need and that your beloved dad will come through with a great recovery as so many others do. As TC_LasVegas reminds us all, "stay positive" with long, deep breaths. Deep breathing is a really wonderful thing at times! Good luck next week and keep in touch. Take care. God bless. Lana