Is that what can be expected?
Not while you have LEDs in series with the motor winding.
It is probably that which is limiting the torque to the motor and causing it to skip.
I decreased the speed to 50; it didn't seem to make any difference as would be expected since you were thinking that the arm was falling short of the start point.
No you are skipping pulses, if it still happens at 50 try it even slower.