Floppy servo controller with pot control

Hey guys!

I've wired a floppy disk to the UNO using 3 wires (one for ground).

The code I had been using that let me control it (somewhat) through the serial monitor came from here: http://www.instructables.com/id/floppy-drawbot/

That's great to move it a certain pre-determined amount of steps, but I'm trying to add manual control.
I'm having trouble getting it to work with a potentiometer though.

Have you thought about using a rotary encoder? It would can be setup to work similar to how you want to use a potentiometer, but without the ADC that can introduce errors.