Check Engine Light On problems of the 2009 Saturn VUE

The check engine lights was supposed to be due to a catalytic converter was a sure fix, I paid 700 to replace and a day after picking up from my mechanic it is doing it again. It was hesitant at first but then it started again and got worse. The rpm accelerating but speedometer slowing down. I took it back to my mechanic, he read something to me about the replacement of converter, it said to drive it for 1 hour at high speeds to burn off inside the new converter, reset the light which should fix the problem. I had already driven for 1 hour because I live an hour away. I head home and as I¿m getting on the entrance ramp to I-75 something came through my vents and in my throat and chest and I start coughing really bad and tightness in chest. I got up to 55mph and the truck started jerking and I noticed the brake pedal was down to the floor and my brakes locked up. It will not go more than 20-30mph. I pulled over to the shoulder and while still in drive the truck will not move. Check engine, abs and traction lights came on. I called mechanic and he suggested I roll down my windows and get some air because I was coughing so bad and have it towed to be safe. Called onstar and now abs codes, told to take in for service within 7 days, I advised her cannot drive over 20mph and requested a tow. A state trooper stopped to assist me, said to get in safer place so he held traffic and drove behind me to get off interstate while I wait for tow truck. 7:32pm in the midst of rush hour traffic and 50 miles from home. I was horrified! I waited 2 hours for a tow that never showed, had to get a ride home again. Eventually got vehicle to a gm dealer. I rcvd a call from the service dept with a quote of $5k of repairs to include a brake job because rear pads were metal to metal. Had brakes checked 1week before and had 30% left, leads me to believe it was brake dust making me sick.