Those weren’t regular occurrences. You don’t need to bring up the most horrible horror stories and occasional myth to know slavery was horrible. I once read “Negros in American Life” by Richard C. Spade. As a most excellent work, I learned that slaves lived in huts with dirt floors. And at one plantation ate nothing but bits of bacon and corn cakes.
The children didn’t wear clothes, they like had no shoes, and they waked in the dark to work all day until the sun fell. Include the whippings, and the auctions, and the familial separation, and the mistreatment, and the mere act of being enslaved, and then you don’t need to use the most extreme instances of horror. Rather, you can stick with the “mundane” aspects. It was bad, without and special cases needed to make it so.