Have you measured your axis to see what the actual torque load is where the motor will mount? Right now we are dealing with a significant number of variables, from gear reduction to friction, and it will be easiest to just measure how much torque is required.
The best way to do this is with something like a fish scale. Just tie a string to it and wrap it around the place that your motor will mount and pull it until the axis begins to move. That will give you your detent torque, and we can figure out what kind of motor you would want from there.