"Does anyone have a solution to leveling a TG that is on a trolly & on uneven cemented in flagstone?"
Designing+Building or purchasing a weather resistant, manually adjustable or self-leveling gimbal base for a ~200 lb. TG can get time consuming and/or expensive. Another option would be to replace your existing TG Dolly fixed casters with adjustable leveling casters. The "poor man's" solution would be to shim-up the dolly with a few patio blocks.
"does anyone recommend a PH Testing Meter?"
I highly recommend the following:
Calibration Solution 1:
Calibration Solution 2 (optional):
We had the six towers on a peace of flagstone 24 x 24, then put shims under it, bought at our local hardware store. We pried up the flagstone and put them under it.
We use a pH tester called Eco testr pH2. It's super easy. My husband researched them and found it.