Oscar-nominated actor Don Cheadle has appeared in more than 100 films and TV shows. But it had been a quarter-century since he appeared on stage in the Off-Broadway hit “Topdog/Underdog,” until he made his Broadway debut this spring in a revival of “Proof.” In this web exclusive, he talks with Tracy Smith about the lessons of his parents; catching the “theater bug” as a child; the “hamster wheel” of an actor’s career; and his emotional investment in works like “Hotel Rwanda.”