Is My Pomeranian Puppy Naturally Aggressive?

Hi,

I have had Harley for a month and he is 3 months old. He is a typical pomeranian in the sense that he is very energetic and can be quite a handful. My concern is that he becomes extremely aggressive at times. When we go out in the backyard, he eats absolutely everything. I can tolerate him eating a bit of grass or chewing on a leaf, but sometimes he will put something in his mouth that is not edible. When I try to pry his mouth open to take it out, he will snarl/growl/bark and try to aggressively bite me. Is this food aggression? Dominance aggression?

I am an avid watcher of the Dog Whisperer so I try to implement Cesar Millan's strategies...using calm, assertive energy to communicate that his behaviour is bad. I also grab his torso to mimic another dog showing dominance but it only makes him more aggressive. I am very concerned that I will have future behaviour issues with Harley and I need to know if a) this behaviour is normal b) will this behaviour eventually stop and c) am I doing the right thing???

Any suggestions would be greatly appreciated...thanks!!