A rough check to see if the rear brakes need adjusting is if the handbrake travels a long way before it starts to work. First slacken off the handbrake cable, then adjust the brakes, then finally adjust the handbrake cables, it's amazing how many time you see someone adjusting the cables and think they are adjusting the brakes, not so.
With regards to the calipers, if the brakes were working OK before the pad & disc change I would first check the disc runout, if the hub mounting face was not cleaned with emery cloth to a good finish then it is posible that there may be excessive disc runout. This can cause excessive pad knock back. If thats OK then the pistons & seals in the calipers may be dry and not allowing the piston to "self adjust". The pistons need to be worked in out out several times to lubricate the seals. This hopefully should cure the problem.
regards johnwr