Do you have any more info on how you actually connected your motor to the threaded drive rod? I'm trying to figure out a simular thing except I'm using a 12 volt geared motor. The motor shaft is one of those half round tips and not a round tip so this might pose a problem but I think I can use your same approach.
You used the nylon scews and inserted that into the spacer but how did the threaded shaft attach to this spacer? Any more detail on the construction would be awesome.