You seem to have a fundamental misunderstanding, tvtech. The input impedance of a VOM in not equal to to the ohms/per volt characteristic multiplied by the voltage you are measuring; It's the ohms/per volt times the range you have selected on the meter.
For example, it would be likely that you would be using a 1000 volt range to measure 800 volts. Then the meter input impedance of your YEW would be 100 megohms, not 80 megohms.
No misunderstandings here. The YEW is not a VOM. It is a 100Kohm per Volt analogue Taut Band meter