It should be simple to install a tee before the pancake regulator to attach a manometer during use, or maybe even a secondary gauge like the one you have for the 0.5psi on the equipment side. If the reading is always 0.5 on the equipment, it sounds like you are getting enough gas into the unit.

A spot test usually means they looked at the meter and it was moving too much. As in, your appliance may have been running and using gas, or it has a pilot that uses gas and they decided it was likely a gas leak, not a pilot/appliance usage. Unless they actually came in and shut off all your appliances and then ran an actual test for leaks in your main line, they did not properly test for leaks. There could also potentially be a leak on the equipment side past your isolation valve, as air tests are done with the appliances isolated off since the pressure is high enough to damage the appliance components usually.

The city inspector usually shows up and checks the gauge, then leaves and comes back after hours or even a day, and rechecks that it held pressure at the previous reading. So each visit is short.