Voltage Drop for Power Supply Testing
Your sentence " I was wondering if my voltage drop due to the resistor's load should be greater than the 10-30 kV range that I am working in" does not compute.

The voltage across your resistor load will be whatever the supply is producing, provided the supply can provide sufficient current to produce that voltage across the load.

The total voltage rating of your series-connected load resistors must be greater than the voltage you are testing the supply at.