Yep you can stop all food that isn't his regular food (100% though) for a few days and see if he stops pooping all over. You can use his regular food as training treats, just make sure you are counting treats into his daily food volume. I might try and cut back on his food by 1/2 c. to see what it does. Really, he sounds like a REALLY excpetional puppy! Just give it some time hon