Right track, Apple! Marines are a subdivision of the Navy, so the Navy Cross was appropriate. Dartmouth, I believe, appeared only in the novel.
Another anomaly in the Senate hearing scene: The senator asks Michael if he was responsible for the murders of the heads of the Five Families in 1950. That scene actually occurred in 1955 (Vito's headstone, Clemenza's '55 Cad and other cars). Still another anomaly: Hagen tells Michael he's opened himself to "five counts of perjury." Since the Five Families massacre occurred in '55, not '50, Michael didn't lie when he answered no to the senator's question--so he only perjured himself four times! And yes, Sonny sure did pull his punches in the fight scene with Carlo. I guess, unlike Michael, he really didn't want to make his sister a widow.