First of all you CANT be intimidated. You cant let the dog know this through your body language either. BE DOMINANT. If your dog EVER shows his teeth REPRIMAND and take whatever he was getting aggressive with away. Return it and challenge him. Once a dog has EVER SHOWN signs of dominance towards me not only will I take things away but I will challenge that dog whenever I can so it submits to me on anything and everything. You need to get control soon as the dog is only getting older, stronger and more mature.
ITs easier to show than to tell people over a computer.
"Life is like a grindstone. Whether it grinds you down or polishes you up depends on what you are made of."
But a Constitution of Government once changed from Freedom, can never be restored. Liberty, once lost, is lost forever. John Adams