Thank you for the great design!
I heated the central shaft up to get the stepper shaft to fit in the hole. Since the heating distorted it a bit, I chucked it up in a drill and sanded it until the skateboard bearing fit. I had some shearing happening during first few tries with the black wire, but on the 3rd try it seems solid. All wires are friction fitted, no soldering. I cleaned the skate bearing with carb cleaner, then aero-kroil (like WD-40).
I tested resistance with the multimeter and it seems that if there is no load on the bearing, resistance could be as high as 900 ohms. If I press on the bearing just a little bit, it drops to under 10 ohms, so I think this will work for my application (LED lights).