Most puppies try to jump and nip. This is normal. The best thing to do is say "No" in a firm voice, or when they jump, say "off". You need a command that lets the dog know what they are doing is not acceptable.
Eating. I also have a four month old and he eats twice a day, roughly a cup to a cup and a half per meal. So 2-3 cups a day depending on his mood. Plus treats and what he sneaks out of the other dogs bowls.
The best thing to do is get the puppy into puppy class and you will learn basic commands and everything you need to know.