At the time of season 3 Meyer Lansky was not a teenager. He was 21 years old and already well known among his peers for being smarter than your average gangster.

Rothstein was indeed a full blown gangster with interests not only in gambling and bookmaking but narcotics and bootlegging. He was an influence on both Luciano and Lansky.

As far as blacks being involved in gangland violence it wasn't until the thirties that the NY white mob interests decisively took over black and Puerto Rican criminal enterprises. It wasn't until the late forties early fifties that the Outfit was able to do the same. In both instances violence was required.

In the 1920s era there had just recently been the Chicago Race Riot. White newspapers of the time expressed outrage that blacks were actually fighting back. Unlike previous pogroms some whites actually died. Everybody bleeds.

Like Richard Harrow, Chalky White is fictional. But he's not as much of a stretch as some might think.