The nation was almost fully funded by tariffs. I have my doubts about the 90% and suspect you simply made that figure up on the spot. And there was no tariff on the south, it affected all states.
But the goal of the tariff was to protect industry growing in the north.
But tariffs were not the cause of the war. As much as you want to pretend, it all came down to slavery. Even the tariff you lament. It was more important to protect honest business than slave dependent industries.
If the southern agri-economy was not slave based, people might have thought it was worthy of protection.
"With most of the tariff revenue collected in the South and then spent in the North, the South rightly felt exploited. At the time, 90% of the federal government's annual revenue came from these taxes on imports."
You must be fun to be married to.
The secession was prompted by the election of the Republicans with their Morrill tariff, spending on improvements in the north, and their fire eaters in Congress.
The war began in Lincoln's office after he discovered that secession would stop the revenue. Secession and slavery were afterthought excuses.