I think milk is okay if your puppy handles it--no gas, no diarrhea from it.
Since your dog likes milk, try mixing low fat cottage cheese in his food....about 2 tablespoons per meal. I make my dog's meals and am moving in the direction of an all raw diet, and most homemade dog recipes call for cottage cheese to be added. Dogs need calcium that they naturally get from chewing raw bones.
Adding "human food" to a dog's diet is not spoiling a dog. Its actually healthy. Just be sure never to give raisins, grapes, or chocolate as they are toxic.
Maybe your dog would eat his dry kibble if you poor milk over it like cereal.
