Might want to post up a few more photos for reference, have you made sure that there's no missing or loose bolts in the brake arm or caliper causing the brake to shift under load?
your going to have to get the disc free from whats rubbing then do a visual check on the rotor to see if its warped, spin the wheel while holding a sharpie marker VERY steady, and close to the face of the rotor, get it closer and closer and see if the marker leaves any marks indicating a warp... if its bad bad, you will just see it visually. but the marker can help if its slightly warped...
I'd hold off rushing off to buy a new bracket before determining for sure it is to blame.
Oh and welcome down the Rabbit hole, hope you have a good tool box full of Metric wrenches!