Hi Tom,
The initial diagnosis is a troubling time, neither you, your dad or indeed his doctors actually know exactly what he confronts until all of the tests have been completed.
So all you can do is take a deep breath and take one day at a time, all will become clear in a few weeks.
Once your dad knows what stage the prostate cancer has reached, it will also be a good time to pause and reflect on the various treatment options, no need to hurry a decision, let him take as long as he needs to make his choices.
When you look up 'survival statistics', bear in mind that they are out of date, science moves on and treatments improve, the treatment I had 10 years ago has been superseded, so your dad's odds should be better than the statistics suggest.
One of the hardest things to deal with at diagnosis, is the worry we cause to wives, sweethearts, friends and family, so try not to trouble your dad with your worries, I know that is difficult, but by the sound of it he has enough worries of his own, and he will tell you what he wants you to know.
I know that when I was first diagnosed I just wanted all my friends and family to carry on as normal.
:)
Dave