It's not a nice possibility, but slaves are renewable, so you can have more work done with raw manpower, which would be enough for small-scale industry if food is cheap enough.
Not really--IOTL the American South was the only slave society that saw slave populations remain stable or grow due to reproduction rather than further enslavement, and the causes of that are pretty much tied to a set of unusual factors in that region (climate, ban on imports and enslavement, etc.)