A small change would be to use the multimeter in current measuring range, instead of voltage measuring.

This way you can reduce the measurement current to microamperes, and it would also be much less sensitive to the impedance of the multimeter. And the voltage on the wires going to multimeter will be less than a volt.

It is still a good idea to leave R2 in place to limit the voltage in case the meter is not connected. You could lower its value to around 1kohm to limit the maximum voltage on the measurement wires.

And like other answers already mentioned, you will have to construct R1 from multiple resistors as a physically long chain, to avoid arcing. For example, 100x of 10Mohm resistors in series would give 1 µA = 1 kV response for the meter.