The buzzing is undoubtedly the stepper stalling because you're trying to step too fast. You doubled the steps/unit, but didn't change the max speed, so the step rate during jog was doubled, and the motors can't handle it. First, reduce the max speed on the motor tuning dialog to a low number, like 10IPM. Then check the jog operation. I think you'll find it works fine, just slow. While you're there, check the move distance is correct. Once both of those are OK, then play with max speed and acceleration, and set them low enough that the motors don't stall.
But, sounds to me like you're really in half-step mode, not full step. Either that, or you have a 2:1 mechanical reduction you've left out of the calculation. For 10-pitch screws, full-step 200PPR motors, steps/unit *will* be 2000 in inch mode.
Regards,
Ray L.