Typical Plan When Post RP PSA goes from < 0.02 to >= 0.02?

I moved out of state since my prostatectomy so for the 18 months following I just did ultrasensitive PSA tests every 3 months. Up to 18 months they always came back < 0.02 but got my first one that said 0.02 (no other digits) instead of < 0.02. My post surgery pathology was "clean" my tumor was in the middle, no lymph node involvement with extended lymph no removal, no positive margins or seminal vesicle invasion. I was Gleason 3+4 but my pre-RP PSA was 29 (however higher PSA is typical with the tumors that are closer in and not at the peripheral of the prostate - but still it's a high risk factor.)

Some studies reference 0.01 as "undetectable" others 0.02 others 0.03 but all levels are extremely low.

I'm fully aware that there can be fluctuations unrelated to cancer recurrence at those low of levels but of course going from < 0.02 to 0.02 is a bit unnerving.

It's going to be a few weeks until I can establish a relationship with a Urologist in my new state so I have a couple burning questions that would be great to get answers to sooner than later.

I was planning after 18 months to go for tests every 6 months but with this slight change, I'm sure it's recommended to continue at every 3 to see if it is going up, at what velocity? Or do many Urologist recommend doing another test say a month later to rule-out lab error? Although when not testing to 3 digits the difference between 0.02 and < 0.02 is quite negligible. If it came back 0.02 or 0.03 though a month later it would at least confirm it was not just an anomaly.

The second question which I admit is pessimistic thinking but still nice to know is, for private insurance, what evidence/results does the Urologist need to provide to get salvage radiotherapy approved? Can people like me, assuming a slow year or more doubling time, still be years out from being approved for salvage therapy?