The fugitive slave act and the Dredd Scott Decision preceeded the sesession of the southern states.
The 1828 tariff of abomoniations was Congress's attempt to show how outrageous the tariff is, which miserably failed. That put the tariff at an all time high, which greatly impacted farmers, who were drastically losing money. Most of the farmers were in the South. Calhoun was born in KY, and therefore was a Southerner. Knowing all this, we can easily conclude that "he was a Southern farmer who was sympathetic to the cause".
A. change in the U.S. balance of trade compared to the change in GDP
It gave us more land it doubled the size of the United States