Mark Thornton (no conservative) makes clear in his study of Southern slavery that it ONLY survived because of government subsidies and support: slave-catching "possees" could dragoon any non-slave-holding southerner into action; courts were "stacked" so as to discount slave testimony (couldn't be offered) or rule against free men of color. Postmasters used state power to censor mails from the north, especially anything deemed "abolitionist." So slavery was deeply intertwined with government power.
To give Andrew Jackson his due, he did say to the nullifiers from South Carolina, his home state:
"If one drop of blood be shed in defiance of the United States Government, I will hang the first man of them I can get my hands on to the first tree I can find."
And still, neo-Confederates complain about Abraham Lincoln!
The Southern post office was one of the more successful pieces of the CSA. Don't be too quick to judge limits on free speech in the South - the North was not a glowing example of constitutional freedom during the War.
To your second point, of course slavery was intertwined with government power. Where there is money, there is power. No different than northern industrialists
Would that be the same Mark Thornton, author of "A New Perspective on Antebellum Slavery: Public Policy and Slave Prices" and "Slavery, Profitability, and the Market Process," who is currently a senior scholar at the Ludwig von Mises Institute and is far better known for his recent book "Tariffs, Blockades, and Inflation," which argues that the tariff was clearly among the "major factors leading to war" given that "Republicans who came to power in 1860 supported a mercantilist economic agenda of protectionism, inflation, public works, and big government"? Just curious.