What to make of this?

Very familiar; I had the same experience.  For the Last 10-12 years my PSA was below 3; DRE normal,  Then, 6 months ago, PSA jumped to 8.1, had 4K test which came back 83% negative, in the following biopsy, all 12 cores came back 50 to 90% cancer resulting in Gleason score of 8 putting me in the high risk category.  Radical prostatectomy wouldn't be done because I was too old (77). 

I assume that you're feeling now, pretty much how I did then.  In the short space of 2 months I went from feeling strong and healthy to feeling attacked by a fast moving, deadly alien inside me, with no idea why and no idea what to do next.  Began to research medical studies and quickly discovered the best percentage of success was the triple modality of Seed therapy, ADT and External Radiation.  In the meantime, my urologist made appointments for me with several specialists, supposedly to help tell me what I should do,  All this took time and which allowed this incredibly aggressive alien to escape.  That killed plan A as seed therapy was no longer possible. 

I've now been on ADT for several months and have just finished 2-1/2 months of EBT and now waiting several weeks of wondering if plan A was successful and if not, what is plan B?

What's allowing me to be happy and free of worry during all of this is something I can't explain; my attitude: "It is what it is". 

I've always loved learning in detail and I seem to have transitioned into studying this final phase of life.  It seems to gives me peace knowing that I'll finally learn the rest of the story.

I'm sorry to bore you with this long story that you're already experiencing.  When I read your post it seemed so familiar, I just wanted you to see how someone else was coping.  My thoughts and my prayers will be with you that you find the peace that I've found.