To expand on 3), the USA blockaded the CSA port of Charleston, SC. This is, legally, an act of war today and was an act of war then. Thus, the USA started the war, contrary to PC myth.
Regarding 2), slavery was a contentious social issue of conscience since before the Revolutionary War of 1776 but wealthy Northern slave traders, not Southerners, kept it politically tamped down. Lincoln became very unpopular because the war was not going well for the North. To turn the tide of public opinion, he introduced the slavery issue, hence his Emancipation Proclamation in 1863.
Regarding 4), the KKK today is a racist, white-supremacist organization but was not originally created for this purpose.