The South seceded because they perceived an economic benefit to so. The North decided to prevent the secession because of a perceived economic benefit. The cost of the war on both sides was much greater than either anticipated.
Since then, there as been a need to justify the carnage in religious and moral grounds and to diefy Lincoln.
It’s like tryng to convince someone that the Trojan War was fought over some chick with a pretty face. It probably had more to do with regional power, maritime shipping lanes and access to raw materials.
The south rebelled against the results of an election that signaled a national sea-change in attitude toward slavery. They lost an election and had a temper tantrum.
Slavery was being phased out amongst the civilized nations of the world but the southron slavocrisy reacted much like Øbongo does - instead of adapting to the changing circumstances, they doubled-down on their unholy investment.
The north reacted in self-defense. None of the rest of what you wrote has any relevance.