I went thru a similar situation, but I had 2 focal point margins and was not negative margins like you. I had a small but significant PSA rise between my 2nd and 3rd year post op to above the .1 level. With your negative margins and still lower numbers, I would concentrate on healty living and diet. Try not to worry and stay positive no matter how difficult that may seem.
BCR was defined as somewhere around 0.20 to 0.40 from what I had read, but now they are also looking at 3 consectutive "rises". With my slightly positive margins and a trend that did seem to rise, I opted for salvage radiation based on my DaVinci's doctors opinion along with the radiation oncologistm, my mind frame, and some other logistics. The current practices seem to be opting for salvage radiation for some cases at the lower numbers now as some studies have shown better outcomes. Thinking the PSA number was starting before 0.50...
Anyway, time for calm and maybe some additional research to help ease the unknowns... The thing you have going for you is you have plenty of time, still low numbers, original clean margins, and future alternatives. And the technology and treatments are improving every day....
I know any PSA rise it is dissappointing... I have been there... I thought since the prostate was gone I would never have to deal with PCa again. Even started to forget abpout scheduling routine appointments for checkups. I forgot that I was a "survivor" and not a person that never had PCa. It took awhile for my mind to switch back to a positive fight mode and constuctive thought processes... To not let PCa control my life, but for me to once again become informed and in control of my life and decisions on living a quality life and as a PCa survivor.