Originally Posted by PeterM1
Doing this on a jack is extremely dangerous due to the force you have to apply to loosen and torque the carrier and the rotor itself. Jack stands are the only option and in general the only use for your jack should be to lift the car onto the jack stands.
Yes, the movement of the breaker bar/torque wrench is from under the car, neither will fit from the top side of the wheel well.
This is really for the OP, but PeterM1 has good advice. I suggest that if you are going to continue to do work on your car that requires it be lifted off the ground, then get four (4) well made, hi-capacity jackstands and the proper extended-saddle floor jack (i.e. extended reach jack to get to the front central lifting point) to properly lift the car from the center jack points so to safely raise the car and set it on the four jackstands. Working on a car that has all four wheels off the ground and the car sitting properly on jackstands that are located at the four lifting points on the rocker panels is just as safe as if the car were on a commercial hoist.
Working on a car that is only on two jackstands with two wheels still on the ground is very dangerous as PeterM1 has indicated. OP, do yourself a favor and get the proper lifting equipment if you are going to tackle DIY projects such as brakes. It is well worth the investment and may save your life too.