Hi, not discouraging direct answers here, but while you're waiting, you may be interested in a few earlier posts
the FAQ has a whole section on The Civil War | Causes, discussing the "main reason", i.e. the right to practice slavery
/u/sowser and /u/ancienthistory in What is the history of the Confederate flag and what does it ACTUALLY stand for?
more from /u/ancienthistory here Morphing views of the symbolism Confederate Flag
I‘ll answer your first question. I think the answer to the second is more of a personal belief than a matter of historical fact.
In the years leading up to the war, the economies of the southern states which went on to form the CSA were almost entirely dependent on agriculture, and therefore slavery. Things had been that way for quite some time. The economies of the northern states were becoming more manufacturing-oriented and thus decreasingly dependent on slavery.
At the same time, a shift in ideology was slowly overtaking the north. Some northern states took a stand and began to refuse to honor their legal obligation to return runaway slaves to their rightful owners and otherwise sought to defy the institution in any way they could. Understanding this, the Confederate states saw that a potential law prohibiting slavery would utterly destroy their economies. It would shift the power in the country from being relatively balanced to heavily tilted toward the northern states.
In the election of 1860 Lincoln did not run on the platform of abolishing slavery, nor was he an abolitionist per se. He slowly progressed toward the viewpoint that a change needed to be made in order to end the Civil War. Remember, the Emancipation Proclamation was made on the first day of 1863 and South Carolina seceded more than two years previous in late 1860, with the first shots being fired in the spring of 1861.
Lincoln believed that the institution of slavery was immoral but as a lawyer knew that the Constitutional issues which could be cited in opposition to slavery were scant. However, the Republican Party (of which Lincoln was a part) at the time was moving toward fundamentally opposing slavery. The abolitionist progress made in the north had led to rising tensions over this issue. While Lincoln may not have forced these changes on his own, the southern states saw the election of a Republican in the pivotal election of 1860 as a large step in that direction.
Their disgust over the result of this election and the uneasiness they felt about the future of slavery led the southern states to begin seceding—something they had thoroughly considered if Lincoln was in fact elected—starting with SC about a month after the election results came in.