Sounds like he doesn't understand who the alpha is. By challenging your bf like that, he is really saying that he thinks she is boss. You should really try the training method "NILIF" (nothing in life is free). Before you give him food, make sure he does a trick for it. Same goes for treats, toys, anything. He has to understand that these things are not his rights, but his priveledges. He should ALWAYS eat after you. Never let him eat dinner before you eat your's. In a wolf pack, the two alpha wolves always eat before the rest of the pack. I would also not let him on furniture, especially your bed. He sees these as places that make him higher up on the hierarchy. Have you taken him to obedience classes? Is he crate trained? You should get him a crate so that he has a den of his own.

Instead of bopping him on the nose (you're right, it might make him sensitive to hands), if he growls when you give him something, take it away and put it away. Then give him no attention for the next ten minutes. The fact that he also growls when he is pet sometimes is odd -- maybe he has a physical problem, or he is sensitive on a certain area of his body? I know some dogs that dislike their backs, tails, or paws being touched. But when he growls, scold him by saying "No!" and leave the room and don't pay any attention to him for the next while.

As for the food -- might want to get him on something better than Pedigree. Pedigree is one of the lowest quality feed grade foods out there. Sometimes low quality kibbles will only promote aggressive behaviour. Think about how you would act if you ate Mcdonald's everyday. Try finding a better brand such as Canidae, Innova (Innova Evo is AWESOME), Wellness, Chicken Soup for the Dog Lover's Soul, Pro Pac Holistic, Eagle Pack Holistic, Go! Natural, Foundations, Healthwise, Summit, California Natural, Solid Gold...etc. Try going to a pet supply store or small pet shop as opposed to something larger.