Hi HLeslie
Welcome to the forum!
Some good advice has already been provided by forum friends so I won't repeat it. The purpose of my reply is to try and give you some hope.
I was 60, one year older than your dad, when i was diagnosed with PCa - over 2 years ago. I was exactly in the same position as your dad at one time - diagnosed and then had to wait for MRI scan etc.
To cut a long story short it transpired the PCa was confined within the prostate. I opted for surgery to have prostate removed and here i am still alive and generally quite well. The choice of treatment will be down to your dad so i am not suggesting surgery will be right for him but what i really want to emphasise is that all is not lost. Your dad will be in good hands.
It is good you have found this forum. There are other daughters and wives on here and for me as a man it is good to hear things from a woman's point of view. If you express here all your fears and doubts i am confident someone will come along to try and give some words of comfort and support.
I get the impression you have a close bond with your dad. If i am right, then i can very much relate to your situation as i have a daughter too and she is the apple of my eye. My guess is your dad is putting on a brave face as that is what dad's do. When i was diagnosed whilst of course i was scared the thought did occur to me that it was better that i had cancer rather than my wife or daughter - i would have found that harder to deal with. That doesnt make me a saint - just a husband and dad!
Whatever treatment your dad chooses will possibly leave him with some side effects - eg urinary leakage. My sense of humour helped me deal with this within my family. There is one side effect that men find difficult to accept that your dad will likely keep very quiet from his daughter but if you search through the posts on this forum it will become clear what i am talking about.
I very much hope the outcome of the MRI scans etc are good.
I also wish you, your dad and family all the best as you travel this PCa journey together. It is easy to say but you are not alone. All on this forum have travelled a similar path and understand all the human emotions involved.