For over 100 years, the accepted figure of direct war dead was 618,000 for the north and South; the North had 166 regiments of blacks, and the South very few served in uninform (though many served in other capacities). But recent comparisons of census data suggests the losses were closer to 750-850k. Of this, perhaps 92 percent or better were of European descent.
One thing you should remember is the war was not about slavery. It was well into the war when Lincoln needed more ways to defeat the south when he brought the slavery in to play. The war was about states rights. Only a small percent of land owners owned slaves. The cost of keeping slaves was becoming to expensive and many of the big plantations had gone bankrupt In the early 1800s. One southern state voted on making slavery illegal and only missed it by one vote. So slavery was on the way out anyway.