What is the relation between hinge moment at the control surface and servo torque?
The servo torque depends on the mechanism. If it has a gear ratio of 1, they will be equal. If the servo is driving larger angular deflections than its own, the servo torque will be higher.

Another important point is to consider the dynamic forces. XFOIL only computes results for steady conditions. Dynamically, the servo may have to bear even larger torques; due to acceleration or gravity.

Finally, unless you really trust your computations, some uncertainty factor can be used to reduce the risks of redesigning the control system solution.