From what I have read only 10% of southerners owned slaves. From 50% in Mississippi and 30% in Alabama to far less in Maryland, Delaware and Missouri. Then only 10% of the owners actually abused their slaves. Most treated them well because they needed the work from them. Slavery was changed to sharecropper after the war, just another name, and they owed so much to the landowners for food, clothes, housing, etc, that they had to stay a lifetime on the plantation to pay their debts. What's the difference? The young didn't want to stay on the farms as sharecroppers so they left and went to northern cities to find work. If cooler heads prevailed, I think sharecropping would have taken over slavery within 20 years. Lots of lives would have been saved.
The only good things that came out of the war was technology, iron ships with screw propellors, submarines, standard rail gauge, better weapons like rifled cannons and repeating rifles. Also more manufacturing of these items.