...the slavery issue was indeed a primary motivation for secession. But this was based upon the misconception that Lincoln's administration would enforce abolition upon the South...
Well, except for the fact that the south, via Calhoun & Co. tried the seccesion/nullification gambit previously in 1832, I might admit your point. Secession is a lot older than 1861.
RE: Berlin's figures, Chapter 5, Table 6, subtract the 84,000 free Blacks in Maryland, the 20,000 in Deleware and the 11,000 in the District of Columbia- which were not part of the Confederacy- from your "southern" total and tell me what you get.
I have read all four.[Leon Litwack, Eric Foner, William Loren Katz, Eugene Genovese]
You might profit by re-reading the first chapter of Litwack's "Been In The Storm So Long" then. I cited Genovese knowing full well the range of his views - He's still germaine & his later opinions don't negate his earlier work.