what it says on the tin, in 1865 Mississippi and South Carolina were already slave majority (55% and 57%) while Alabama, Florida, Georgia, and Louisiana all had slave populations over 40% (45%, 44%, 44% and 47%) this doesn't cover any free black populations, any ways with-out freedom and the mass movement of blacks out of the slave to the north and west starting in the 1870s, would more of the south become black or even slave majority? would all of the CSA over all become black majority? if so how long might that take? if not why not?
No, I don't think so, and in fact, I'm afraid that the Confederacy, at least under the leadership of certain elements, might possibly be quick to take drastic measures if they even *think* that there's a population surplus danger; maybe not quite on the level of what happened in TL-191 but it could be pretty nasty, nonetheless.
As for expanding the definition of "whiteness"? Even IOTL, for the most part, only white Anglo-Saxons, and Scots-Irish Anglicized enough to be considered "Anglo" were usually considered to be fully "white" by the people that mattered down there in the South(there were a slight few exceptions, namely the Taliaferros and those descended from the Huguenots, but for the latter, most of those family trees outside of a few spots had mostly blended in with the rest of the population anyway....same was true for the Taliaferros, too.).
I'm not saying this can't be done, but it would likely require a fairly liberal(for the CSA, probably centrist by Union standards) party to win an election at some point.....which would be hard to pull off, unless they were able to stoke populist sentiment.
An independent CSA would likely have a significant white emigration to the USA and a much smaller black emigration - I doubt the US would be welcoming to black immigrants if they're not citizens. Add a likely higher black natural growth rate and the CSA could easily become Black majority by present day - they were already 40% black in 1860. It's more likely though that the CSA would collapse before that into black and white majority countries (with the later likely rejoining the USA).
It really depends on the situation. I can actually honestly see many Americans, in the vast majority of scenarios, being at least somewhat more tolerant of black folks, even if mostly because they feel sorry for the slaves(and ex-slaves who managed to escape their bondage to arrive in the U.S.).....and any state gov't caught sending any escaped slaves back to the C.S. would definitely be met with at least some protest.
That would be hard to imagine in a post-Civil War world. Huge numbers of poor whites fought on the side of the Confederacy. The slaveholding minority recognized that it needed the political support of poor whites to maintain its social and economic dominance.
To some extent, yes, but many of these people had no choice, as they were drafted.