Steering Wheel Vibrate problems of the 2012 GMC Sierra

I have goodyear wrangler sr-a 265 60r20 tires on my Sierra denali hd 2500. I was on the way back from nc via I-95 and pulled over so my wife could nurse our 3 week old. Me and the boys went in k-mart for a few minutes. Upon returning and getting back on the road, I noticed my car was pulling bad right and the steering wheel was shaking very badly. I managed to drive it the additional 30 miles back home. When I started the truck the next morning, the steering wheel shake was too bad to continue anywhere but the dealership. I drove to the dealership and they said that the tires would be covered under my existing "bumper to bumper" warranty as the dealership noticed that there was a huge bulge in the tire which was causing all of the commotion. Upon further inspection, it was noted that the front right tire also had bulges, these in the sidewall where the tire meets the rim. The dot batch number is #pj6ka5iv 32/11 and both tires were from the same batch. I was driving around with two defective tires!!!!!!! with my 8 year son, 4 year old son, 3 week old daughter and my wife. This is unacceptable! our lives were at risk! imagine my surprise when the dealership called the following morning and said that gm had "changed their policies and they would only be giving me a 30% discount. " I understand policy but these tires only measured little wear and should have at least 55% more tread life based on the exact tire measurements. Instead, gm is using a sliding scale for mileage that does not take actual measurements into their assessment. So now, I am out $350 for 2 new tires that should have lasted a whole lot longer and no help from goodyear or GMC.