Sitzu puppy-- does not listen, dog training?

He is abut 2 1/2 yrs. old and does not listen sometimes. When the door opens he bolts out the door, leaves, and does not come back for hours. We have to run and get him. He absoulutely loves dog biscuits, we have to bribe him!! He does not sit or set or stay well, and gets very aggressive when he wants out, a car drives by, has a biscuit, and when he has his toys. He has even bit my little brother through skin. He is stubborn!!