Is he peeing or pooping? Or both? I don't have much good experience in this deptment but - ??after he has gone in the house could you clean some of it up (soak the urine with a old rag etc./ put the poop on paper ect.) and bring it outside where you want him to go. And everytime you take him out bring him to that spot and let him smell and he might start going in that area. If he is peeing could he have a bladder/kidney infection? If its pooping could it be the food? Do you take him out right after he is done eating and after playing? I hope something works because I am sure you are heartbroken about having to return him and your parents have the finally say so I can see why you are desperate to get this under control.