I don't think you're getting off topic. Certainly there were other issues, differences & tensions between north & south. Perhaps, if not for slavery, civil war would have developed for other reasons.
But while tariffs, taxes & other issues did divide north & south at the time, I don't see them as casus belli. And certainly, according to Confederate leaderships' own statements, they were not. Slavery was. In their own words.
Not sure what you mean by Lincoln appearing more bigoted than Davis. Lincoln personally opposed slavery (though he also believed that as POTUS he had no right to interfere with it) while Davis passionately supported it. I suppose you could argue that Davis did like black people more—as slaves. Lincoln, the westerner, had no real knowledge of or contact with them at that point.
And yes, the south did try to secede peacefully. But Lincoln warned them that war would entail if they voted thus. And I think he was right. Secession as I wrote would have led to anarchy.
Incidentally, have you heard of Seward's Albany Plan? Before he & his allies had Lincoln's measure they believed he would be a powerless figurehead which would allow them to let the south go, while the remainder of the US invaded & conquered Canada.
Obviously & thankfully things didn't work out that way.
And yes, I agree in early Reconstruction blacks in the south probably did have more rights than freemen in the north. But, bear in mind, too, that Union soldiers returning home from the war can't have been too happy to compete for work with freed slaves who were used to working for free. In fact, Confederate apologists argued that slaves were better treated than industrial workers because the former were cared for from birth to death by the master/owner, while workers were only paid when they could work. The bosses, otherwise, owed them nothing. It's one way to look at things, I suppose.
But, getting back to freed slaves in the north, such a shift in social relationships is a strain to any society. Many congressmen voted against the 13th amendment, which ended slavery, because they didn't know what to do with four million free blacks. I suppose you could argue that that problem persists to this day. Lincoln believed they would be better off emigrating to Africa. He believed they would never be accepted into US society as equals. Some civil rights leaders today might agrree.
I think if you look at Gen Sherman's order #25 granting land & resources to freed slaves you see the tragedy of Lincoln's loss, because I believe he would have endorsed it, while Andrew Johnson did not. We'll never know for certain.