Maybe Lincoln should have just let them go.
I guarantee you that when slavery was over the Africans in the Confederacy would have been repatriated back to their homeland.
Yet, Lincoln didn’t tell his entire plan to the US; I loathe slavery because any man should be paid for his work.
As for splitting the nation, it would have left the United States too vulnerable to invasion. As shown, the Confederacy would have had few weapons and were not the most armed people. They concentrated mainly on agriculture and culture, not arms and they were not practical in a lot of areas. I believe that Confederates were not going to be able to defend themselves from invasion against any country.