Getting Stubborn

Maybe it's adolescence?

I've read dogs tend to "test" the boundaries and limits they once accepted without question.

Basically, now he's asking questions. What if I don't get off? What if I "talk back" and say I don't want to move?

I know 2 years old sounds old for this, but I have read that adolescence can last until 3 years old. Depends on the dog.

Either way, I think it's just the dog starting to say "what if I don't?" or "I don't want to and leave me alone!" Keep enforcing the rules he has and maybe even limit what freedoms he used to have.

Anytime there is a significant change in personality or behavior, its time for a vet visit.
I assume you've never done the training of move, come, get off, etc and have to physically move him? The aggression...I prefer resentfullness...only gets worse under that method as it becomes a constant battle of wills with some serious side effects. ie: some youngster will try to pet/move him and it won't be pretty.
Go back to all the puppy school basics of come and move. Use those luring techniques and don't forget the treats and praise for reinforcement.

I would advise to look at leadership. Now that he is two years old he is a contender for the role of leader of the pack, and becuase you are the current leader he is testing whether he would be able to take over from you. Show him a strong but fair front and he will accept your leadership. If you have doubts about what you should do to gain and re-assert your leadership check out a woman by the name of Jan Fennel also called the Dog Listener, she has an excellent, gentle, proven method at gaining and keeping leadership over your dog.

Good Luck