First Tube Amp: Advice? Keep spare tubes on hand?

You have been given great advice mine is don't be afraid of the multimeter(DVM);very easy to use and a very needed tool for manual bias;also checking blown fuses that look good but don't ohm out as a short and read open.

I don't know how your amp is setup to bias; it maybe a tube at a time or pairs or quads; I would talk to the manufacturer and tell them what you are measuring;then go from there.
If this were my amp I would move tubes from left to right channels to see if the measurements move or change;also inspect the pins on the tubes for oxidation;could be some buildup that needs cleaning as well as the tube sockets themselves.