Dave, in a similar position trying to decide, but definitely going for radiation. My only suggestion it to consider Orgovyx instead of Lupron. The only drawback also the advantage is that it is a pill so each day you'll be tempted to forget. But read about it because this is an inexperienced suggestion.
Proton 5 fraction looks like the best choice to me, but California Proton isn't presently offering the 5. And I wonder how the 5 fraction proton compares to 5 fraction photon. Especially since photon can be a MRI guided procedure. You must have researched Proton. How did you decide Proton vs Photon.
A second suggestion (ok I have two) is to have the Decipher genetic analysis of the tumor itself. It softened the blow of the biopsy results and may change your course. They use the biopsy material already drawn.
best wishes