I think it is quite accurate and simple method to measure offset. And I don't know why you don't have Mismatch contribution in the drop-down menu. It should be under the 'Sensitivity results'. Are you sure you ticked the 'Save Mismatch Data' at the MC options?
If you want to save the signals under MC simulation you should tick the 'Save Data to Allow Family Plots'.
We don't know too much about your project to say yes you need an other comparator. We don't know the
application, the speed, consumption limit, etc.