I had been undetectable for 18 months straight after surgery then this past January, I went to 0.1. I had a retest 2 weeks later and it didn't change. Then I had another retest 6 weeks later and it went back to undetectable.
I would say wait for 4 weeks like your uro said. You don't show what your original PSA was before treatment. Mine was 18.5, I have 2 positive margins and my staging is like you, pT3a.
So all things considered, our stats are similar.
I hope you have my luck and drop back to undetectable.
Bill from Florida