I read the article at your link. It rebuts nothing. It asserts 29 million dollars worth of wool imports balances the ~300 million dollars in Southern Agriculture product exports because Northerners wore wool.
It is an analysis written by a child, not someone seriously addressing the issue. It is the opinion of someone intent on dismissing the claim without putting forth any real effort to discredit it, knowing full well that the vast majority of his Union supporting audience wouldn't bother to critically dissect his claims.
There is a simple fact that remains. Imports coming into the Country have to be paid for by Foreign money received, and since that comes mostly from Domestic exports, you have a conundrum explaining how all the Northerners got all that European money to pay their share (80%) of the tariff duties on imports.
Since Southern Agriculture products made up 75% of exports, where did the Northern states get their European money?
So now are you saying that the cotton states were not paying most of the import tariffs, but are instead arguing that southern exports provided the foreign currency to purchase imports?
Very little of the cotton crop was sold directly to European customers, just as very little of any commodity product today is directly sold to the final consumer today.
Northern merchants bought most of the cotton crop and paid the planters in US dollars, not foreign currency. Those merchants then took on the expense and risk of shipping and warehousing that cotton and selling it on the global market. When they sold that cotton to foreign buyers, they got the foreign currency which they used to purchase foreign goods, while also paying the tariff on imports. That is why the lion's share of tariffs were collected in New York.
But the number is not 75%, it's 58% consisting of:
Bottom line: Exports of Southern slave-grown cotton & tobacco were certainly important to the nation's well-being, but they were far from 75% or 80%, or even 90% as some pro-Confederate posters have claimed.
More important, as it happened, when Confederate states halted production and export of cotton, both the world itself and the US Union economy quickly adjusted and found other ways to make a living.
So those slave-power planters turned out to be less important than they had imagined themselves.