You left out only one important FACT which is that {{{{{Slavery}}}}}} would have rapidly died under it's own weight had the south been allowed to fully develop economically.
Yes! In Maryland, the number of free blacks increased as farms in the vicinity of Washington DC and Baltimore stopped growing tobacco and shifted crops to the even more lucrative produce farming to supply the cities. Slaves, not needed for the less labor intensive crops were freed, often taking the name of either their trade or adopting the last name of their former masters. Such relationships had not generally been adversarial, (Recall if you will,
Uncle Tom's Cabin was a novel and sensationalistic abolitionist propaganda.) but often were close. Many owners, sometimes in defiance of the law, taught their slaves the rudiments of arithmetic and to read and write, as such were useful skills.
Slaves were expensive, required initial investment, plus they had to be fed, clothed, housed, and given some sort of medical care or that investment would be lost--whether they worked or not.
It was not unusual that the owners wouldn't let them in the hold when loading cargo on a vessel, because the slave might be killed (and the investment lost). Instead, some hireling would be down there taking his chances (usually Irish, but any fresh immigrant would do, or even a local).
(It's no accident the Irish (who need not apply) ended up in jobs like longshoreman, teamster, powder monkey, policeman, fireman--all the most dangerous jobs of the day.)
The idea that it was cheaper to hire a fresh immigrant and let them procure their provender from their wages wasn't lost on the slave owners, and the institution was becoming less relevant.
The more industrialization, the fewer slaves.
