If your machine moves one inch when you command once inch, then your 0.0001525 would be correct. If not hit "C" at the Step increment menu item, and you will be given a simple table to fill in and TCNC will work out the mathes. If you are currently commanding one inch and getting 1/2" then the driver is probably set to halfstep. Half stepping should reduce resonance problems a little.
The fact that the machine is slow and looses steps at faster speeds (I am assuming this is the underlying problem), is probably due to gutless 45ozin high inductance steppers run at low voltage. Remember that the althread is pretty low efficiency stuff, turning about half what little power power you are feeding it into heat (although it is being feed so little power that the althread can disappate that heat without getting noticeable warm).
Sorry to be blunt. What are you trying to move?