>>2931511
>Below a certain speed all feedrates seem to. be trwated the same
It could be that you're running into integer rounding issues, though that doesn't seem quite right, especially not with Marlin 2. Have you done a custom build of Marlin for this machine? There may be a setting in there about minimum feedrate. Even if that doesn't fix things, it's still a handy idea so you can set certain GPIOs to output high-speed PWM. That's what I did for my Ender 3 V2 laser engraver. You could also try some other software, like GRBL or whatever.

My idea for an EDM driver is as shown. I'd store energy in an inductor by keeping Q3 turned on while alternately turning Q1/Q2 on like a buck converter to reach a desired current. Then the g-code would release this energy into the workpiece by turning Q3 off, making a big voltage spike at the inductor until it flashes across the tool. I think you could make it produce bidirectional pulses by making it a full H-bridge, but that would require more HV-rated transistors.
The important part of my design is that it doesn't require an expensive AC-to-DC converter, any existing LV supply like an ATX or even a deep-cycle lead-acid battery would do the trick.

2kV sounds challenging to switch, though these days with SiC transistors it's hardly out of the realm of possibility.