According to Richard Rankin, whom I believe you also know, I can give you some information he told me. The "restaurant" was a Speak-Easy during Prohibition. The neighborhood was called "Holy Square", in reference to the Park and surrounding churches. And most of the residents were members of First Presbyterian, First Baptist, 2nd Reformed, and Holy Trinity. The Park Lane building was THE most fashionable and upscale building in Hackensack during it's day, and probably into the 1940's. It was considered very high-end, and many people relocated there from NYC. It wasn't until larger buildings were built with new safe-looking elevators and parking (in Hackensack and elsewhere) that the building went from high-end to moderate. However, during that time there were a great many elderly residents living there who had lived there for decades. And now it is fair to say that it is a working class immigrant building, filled with hard-working people.
Note also that Park Lane was somehow exempted from Fire Escape regulations, but it remains in NON-COMPLIANCE with the specifics of those regulations.