I do plan to test all the ideas out on the motor and I will use the one that produces the best results.

However, I have never used Mosfet before. It is my understanding the Gate voltage must be higher the Source voltage inorder for the mosfet to power the motor. Is this true? Or can I use 5vdc on the Gate of the MOSFET to power 50vdc on source/drain.

1.) Homeade Digital Pot with discrete components connected to the base of darlington

2.) 0-5V amplified by 10 to the base of darlington transitor which will source the current for motor

3.) PWM MOSFET control by an 0-50Vdc OpAmp Comparitor. I will use the comparitor to power the gate on the MOSFET.

Did i miss anything?