>>>And yet in 1860 there had been no “usurpations” or “abuses,” and the Deep South did secede “at pleasure.”
This made their secession unconstitutional.<<<
Your ignorance of history is remarkable. Check out the tariff immbalances between the North and South, that got so out of hand that Yankees could purchase some goods from England and sell them to the South cheaper than the South could purchase them directly from England.
Tariffs were uniform in the both North and South. However, if you're referring to the fact that upwards of 90% of all tariff revenue was collected in Northern ports, indicating that the overwhelming majority of all imports were destined for Northern consumers then you are correct and there was an imbalance. The North paid the bulk of taxes on imports.
If your claim is that the South paid a higher tariff than the North did then you're incorrect in that claim.