Yes the Mayoclinic prostate group is a place to pose your questions and ask for the thoughts of many knowledgeable people in that group.
It looks like you've had a recurrence (BCR) - sorry about that and it is upsetting. A PSMA PET scan has a 50% chance of detecting PCa when PSA is 0.5, so if nothing was detected at 0.7 it is not unusual. I understand that some RO's let the PSA continue to rise until the PSMA-PET scan detects something, so that any salvage radiation can accurately target the location of the PCa.
After my RP, salvage treatment occurred soon after my PSA rose to 0.12 (about a year after). At this point hormone therapy and radiation was initiated. This may seem early, but based on my Gleason score and other factors I was high risk - so hit is hard, and hit it early. The radiation targeted the prostate bed and pelvic lymph nodes as the BCR was most likely limited to this area. After 33 salvage radiation treatments and 6 months of ADT, my PSA has been below 0.01 for about a year now.
In your case, at a PSA of 1.3 the PSMA-PET should detect something (unless you have a type of tumor that doesn't express PSMA, in which case a different type of PET scan is needed). Based on my limited experience and layman's understanding, without another PET scan, I am not sure why your urologist says your survival is 5 years. There are many effective treatments available now that give us realistic hope to push this disease back into remission, or at least manage it for many, many years.
