Regarding the measurements in the manual:
If you do the Ohms Law with the resistance values given for the output valve circuit you'll see that either the anode voltage or the HT voltage given topside of the primary winding in the manual pertaining to that valve is wrong anyway.....17.6mA screen grid current anyone.
Similar for V4.
Probably to do with the range the meter was set to but little to do with it's input resistance.
Lawrence.