lastchancename:
OK, you'removed the smarts from the servo.For one direction control & speed, you need to use PWM with a MOSFET or motor-driver shield.
For bi-directional control & speed, you need use PWM with an H-bridge or H-bridge shield driven with PWM
@wcirvin All the stuff in blue is in the "smarts" in the servo - the part that you took out.
I reckon, if you can't re-install the "smarts" in the servo you have already got then the most practical solution (time, money, convenience) is to buy another servo and properly convert it to continuous rotation.
...R