Ok as you are already getting 1 inch movement when you command a 1 unit move then really all you need to do is go to config menu and then Default units. Change that to Inch and you should be fine.
The problem you have been getting is you have it set to metric but you have entered the amount of steps per unit to equal a 1 inch move. So when you command a move of 1unit you get 1 inch like you expect. Problem is Mach is thinking its only 1mm so you load the roadrunner and it seems fine but when you load your code it is 25.4 times bigger, the reason is your code has G20 in it telling Mach its inch and for a move of 1 it needs to move 25.4 times the normal unit. The reason the Roadrunner is fine is because there is no G20 in it
I suspect your screw is 5 start 1/2 -10 which would mean 2 turns of the motor would move 1 inch so 200 steps x 10 microsteps x 2 turns = 4000 steps per unit.
You have it close to that if I recall but really the number should be 4000 if the screws are accurate.
Hood