Hi,
Your driver and microstepping sound about right as does the ballscrew.I guess my actual question is "Is the inductance of the stepper motor the issue?".
If so, what would recommend for replacement steppers?
I would guess that 11mH will prevent your stepper from performing at speeds much over 100rpm. Low inductance is mandatory for steppers to operate
at high speed followed by highest possible voltage drivers.
For 23/24 size steppers look for 1mH-2mH and reject anything above 2mH.
For 34 size steppers look for 2mH-4mH and reject anything above 4mH.
Craig