First off do not withhold water from a puppy, they need water available 24/7. If someone told you withholding water helps with potty training they are full of it, as that is a myth. So for your food question, feed him three times a day and about 1/3 t0 1/2 cups each feeding until he is about 6 months of age then go to twice a day. If his poop is soft or runny reduce his food a little, if it is hard increase his food a little so it becomes normal. Hope that helps.