Finding geared stepper motor speed
You almost certainly have a 200 step/revolution motor with a 10:1 gear reduction...that is where the 0.18 degree per step comes from.

Your pulse speed is 2000 Hz....so, the actual motor is spinning 10 revolutions per second.  That is 600 RPM.  Then the gear head reduces the RPM by a factor of 10.  So, you have 60 RPM at the output shaft.