Hey Andy, sorry to hear of your present situation. I do agree with you that radiation might not be advisable, but you should definitely seek out the best RO you can to see if this is the actual case….you never know.
As others - and I - have oft repeated: surgery after radiation is not a good idea. BUT, it can be done by a skilled surgeon. Evidently, you have cells resistant to low dose brachy, and they did not die off after treatment. So prostatectomy, while challenging, might still be your best option; also lymph nodes could be removed to check for spread.
Again, it is essential that you find a surgeon who does this salvage surgery regularly and not just an excellent prostate surgeon - it’s a whole different ballgame and you don’t want the SE’s of the surgery to make you miserable.
Perhaps others on the forum can guide you to a center of excellence/surgeon who performs this procedure. Best,
Phil