The author's purpose (to me) is to showing the terror that the British were causing during and after the Boston Massacre. He/She was trying to connect you with the feelings of confusion and the feeling of control. (This is my opinion, it may not be correct but it is what I feel the author's point is.)
Goods and services like food and spices
The Supreme Court case of Gibbons vs. Ogden was about interstate commerce, which is trade between states. (SCOTUS ruled that the federal government had the power to regulate interstate commerce, but that doesn't really matter).
Basically, "interstate" means "trade between states, while "intrastate" means trade within the boundaries of a state.
