The gate scene at Los Alamos is accurate and Richard had many more pranks that he pulled while working there. Most notably he picked locks. The one unique combination of locks was a series of file cabinets in a mathematicians office where the combinations began with the first few digits of the natural logarithm of e.
The abacus scene is also accurate but Richard is quoted as saying from "Surely You're Joking Mr. Feynman" that he knew logarithms so he could calculate the cube root of 1729.03 unlike the man with the beads.
The scene where Richard breaks down after seeing the dress is supposed to have happened before he comes home and happens because he realizes that he has caught himself thinking about Arline in the present when she has passed on. This is mentioned in "Surely You're Joking Mr. Feynman."
Michelle Feynman, who played "Sewing Girl on Train" is the daughter of Richard Feynman and Gweneth Feynman.
Screenplay was written by Patricia Broderick, Matthew Broderick's mother. She was also a producer on the film. Matthew Broderick directed.