Brake Noise

Ok i Have a 08 Impala with about 75,000 miles on it i recently had to replace a wheel bearing because i hit a curb that fixed the noise that was causing. Here is the whole story at about 68,000 ot so i replaced the front brakes while replacing them one of the pistons on the driver side caliper fell out long story short got it back in air was in the system bled the brake that the piston pooped out of few days later started hereing a scraping noise at slow speeds when braking took apart greased everything noise went away. Hit curb replaced wheel bearing put back together scraping noise caome back with shaking of the steering wheel upon applying of the brakes. Took apart cleaned everything turned rotors put back together shudder stopped noise remained. Replaced all pads at about 72,000 again returned rotors noise goes away few weeks later noise comes back worse than ever took to dealership said everything looks fine couldnt replicate noise showed them noise n they fixed something completly different from what was needed noise still there had brake system flushed n filled now slight shudder upon applying brakes above 35mph and a scraping noise is heard from when coming to a stop from about 15mph to 0mph under normal brake pressure when heavy pressure applied no noise and when driving a scratching noise is heard from driver side like wear indicator is scratching the rotor. Please help noises driving me crazy and all shops cannot seem to diagnose the problem

How can we diagnose a noise like this from here, glazed pads, improper rotor surface, hardware not lubed ,are all in the mix, someone knowledgable has to get into this on site.