Lights dim on a switch that was a 3 way
Significant change to the original problem:  The lighting dimmed because the current regulator in the fan burned (or was burning) up.  I took it apart and found significant charring and plastic deformation inside.
I bought a similar model from ReStore and Frankensteined the two together into one working fan.
The three way switch had no impact on the fault as should have been noticed since the observed fan speeds only slowed when the light was turned on.
Thank you to those who read my problem and tried to help me solve it.