If I understand correctly, the way that a screenplay is formatted takes care of all three simultaneously. The font is monospaced and the text size, margins, and line spacing make one page of dialogue pretty close to one minute of time.
This was omitted from the piece, but we count words and then convert to lines at ~10 words/line. When pop culture talks about dialogue in film, we use lines. So that felt more natural than "# of words spoken."