When Flavia picks up the bundle of papers in the rain, it is thick and covered in paper. When she gets across the street and gives the papers to Blind Mac, they are uncovered and the stack isn't near as thick.
There was never an elevated subway line on Tenth Avenue. The closest was the Ninth Avenue Elevated Line (closed 1940).
Flavia brings home a loaf of "dark bread, your daddy's favorite", as her mother says. One look at the wrapper clearly reveals it to be Wonder Bread, which at the time made only white bread.