As for the Civil War not being about slavery, you might want to check with the declaration of secession.
“.. increasing hostility on the part of the non-slaveholding States to the Institution of Slavery ...” is listed as the main cause. It goes on at length about the north not enforcing the return of fugitive slaves, and of working to eliminate slavery.
Tariffs and taxes are not mentioned in the declaration.
did a quick look: I see in the confederate succession of Georgia they talked about the act of 1846 which lead to the Morrill Tariff.
The reason the UNION went to war with the South had nothing to do with slavery, at least not slavery regarding black people. Why did the Union invade?
Tariffs and taxes are not mentioned in the declaration.
Those declarations were only a few in Number, Slavery is only prominent in a few of them, and of course you have left out the ones that do mention tariff's and taxes because that does not suit your preference.
This one quite clearly says that the economic destruction perpetuated on the South by the North is the primary cause of their discontent with the existing government.
http://www.civilwarcauses.org/rhett.htm