How large (mass) are the CMGs on the ISS? What is the minimum torque they apply? What is the maximum torque they apply?
The L-3 Communications Control Moment Gyroscopes (CMGs) used on the ISS have specifications detailed in the L-3 CMG Control Moment Gyro datasheet. Here are the properties you are looking for:
Weight 600 lb., 272 kg
Maximum Output Torque 258 Newton-meter
It's not specified, but I see no reason why the minimum torque wouldn't be zero.