I don't know if Design For Living (1933) has been mentioned. Miriam Hopkins (who was born for Pre-Code films) can't decide between Gary Cooper and Frederic March, so she decides to live with both of them. And of course The Story of Temple Drake from 1933 (also with Hopkins) dealt with rape. That film may have been responsible for creating the Code.
Hopkins was one of a kind and she was really in her element in Pre-Code films (but also did some fine work once the code was enforced).
As for responsible for creating the code (I believe you really mean the code being enforced in July of 1934); Well I would like to credit Hopkins more so than Mae West!