Scooter--no sense in dredging this all up for the umpteenth time; I doubt wither of us will convince the other and while the discussion can be fun, it is not so for those who refrain from participating.
That being said, I did want to raise one point regarding the expansion of slavery into the "territories" ; that southern position was based, to a large extent, on a concern that the northern states could push to colonize territories, declare them "free" (and thus not somewhere many southerners, especially those who held slaves would want to go), thereby shifting the balance of power in congress. One need only loon00k at the compromises reached in the early 19th century which did little more than guarantee that balance would be maintained. A separate CSA would not have the same interest in keeping the balance because they are no longer part of congress what congress does would be more or less irrelevant to them. Might some want to expand using the same "manifest destiny" BS? Sure; but I think many others would want to stabilize the new country first.
As for a pro slavery USSC; my guess is a number of pro slavery justices might well have resigned and gone with their states into the new country; further, a Congress without the bother of the southern states could have passed any amendments it wanted, be they the outlawing of slavery, granting of suffrage to men of color, etc.
I'm not saying the split would have been easy---and the rhetoric would have been deafening on both sides; however, I do think it possible for a more or less amicable split to have been negotiated before the north threatened to invade the south and the south fired on fort sumter. But like with a lot of things, the loudest voices prevailed on both sides, and we were plunged into a costly and catastrophic war instead. And the north/south divisions still remain 150 years after the end of that war.