I would have done one thing differently. I would have very carefully soldered an extension on that worm shaft, lengthening it all the way back to the motor shaft, with 1/16" clearance. A piece of Toyota #0 hose would connect motor and shaft.
That would eliminate noise from the horney balls, but even better, it would have eliminated chatter noise between the gearbox and the brass rotation restrictors. The radial force on the hose and motor would be negligible, given that extremely long lever arm. The ball bearings would resist rotation of the gearbox noiselessly.
