CMH Group selling problems rather than used cars

I purchased a pre-owned vehicle from the CMH Midrand branch and they have been nothing but unprofessional and under-handed. From the initial sale there was issues as the salesman disappeared and then the car wasn't ready. Then on the day of delivery following a Dekra 101 point check and being serviced there the car was presented with the large crack on the windscreen, a plug in the tire sidewall, the lock hanging of the passenger door and the seat belts for the back seats hidden. After complaining and waiting there over 3 hours with my wife and 1 year old, the car was given to us with the understanding if there was any further issues the dealership would sort it out. The car was booked in twice thereafter as I complained about the brakes, a cloud of white smoke, the battery and various noises and issues. The minor issues were resolved (battery replaced, tightened shocks and nuts) but the smoke and brakes weren't. At the recent service under 6 months from purchase the brake pad and brake disc were found to be worn to a critical condition(disc beyond skimming), when I contacted John Grey the dealer principal as the managers and staff had changed, he said they did what they could and its not their problem I could complain to the MIOSA as they had done all they could and were more than fair. Is it fair that I have a R5000 bill on a vehicle under 6 months, had to take the car in numerous times, not sure what other problems await me as the service technician suggested another 101 check and will get a lower resale as issues are found? Is this a fair treatment and is CMH Group happy to stand by such a sale? Should anyone trust purchasing a vehicle from CMH if this is how pre/post sales and complaints are dealt with?