After these discussions it seems best to separate the switch and voltage divider functions. Yes, all three terminals on the potentiometer are involved in this circuit. A potentiometer that appear useful is the cermet Vishay P16 shown here:
https://www.digikey.com/product-detail/en/vishay-sfernice/P16NP222MAB15/P16NP-2.2K-ND/1587862
However, its power rating is only 1W. This would require me to drill an additional hole in the motor enclosure to mount a small switch and a circular pattern is likely to be best. The 3A/125V GC Electronics 35-406-BU may suffice:
https://www.digikey.com/product-detail/en/gc-electronics/35-406-BU/35-406-BU-ND/2041868
I am in the process of sketching the circuit but other priorities exist.