Update 12/19/22:
PO4: It has been reasonably consistent with 0.02 ppm daily dosing (via top-off) but I think I should feed more, add more fish, or dose more. Leaning toward adding more fish

NO3: Looks like the bio-media in the canister filter finally has a stable population of anaerobic bacteria.
My testing setup is not very pleasant to look at but the testing is quick and easy since everything is labeled and ready to be picked up.
It slides into the cabinet like in the picture below.
Recently got a CO2 meter. The CO2 level near the tank went above 1000ppm only once in around one month.
Luckily, I have never had a PH reading below 8.0.
Also, I think the bubbling chamber (with air feeding from outside) is helping to raise the PH level.