Is there another more official theatrical term for “straight man”?

Solution 1:

Straight man is the term that tends to be used for that role in the theatrical community. From the The Methuen Drama Dictionary of the Theatre, at the end of the entry for stooge:

A straight man, the serious and sometimes bullying member of a two-man comedy act, differs from a stooge in being less of a victim.

The stooge is a related term, but note the way the dictionary distinguishes from a straight man: a stooge was an originally Vaudevillian performer who fed a smart alec and took a lot of abuse; a straight man keeps composure in the face of someone else's goofiness, and practices deadpan to elicit humor.

Straight woman is sometimes used as well, as seen in a New York Times theater review:

Ms. Goldberg, whose presence is less frantic and more deliberately centered, is instead the sardonic straight woman to the chaos around her.

That said, note that straight man and straight woman also has a different meaning outside of comedic duos, referring to someone who is heterosexual.