jogging speed limited to 4000mm/m

Ok, now let's look at it from the other point of view:
It is a machine with plastic parts, for hobby use, so not rigid in any way shape or form, so cutting at 4m/m will not be possible ever, maybe for styrofoam at low depth...
My advice, start cutting stuff, stop chasing ghosts, if you have the scaling right, move on, lower the velocity to 2m/m as it will not make a huge difference in time but will be much safer from skipping steps.
After you get some experience, you will be in a much better position to decide what to upgrade or change.
Yeah, and we want pictures/videos of making chips...