The AP is a poor source for a typographic style guide. They are a wire service not professional typographers, and my speculation is that their conventions come from a context of typewriter manuscripts rather than properly typeset books. They eschew en dashes and use hyphens to indicate ranges (e.g. 10-20 instead of 10–20) – something no professional typographer would condone – because they are expecting someone with a typewriter to only be able to type hyphens, whereupon the choice is either one hyphen or two. So in a manuscript you get spaces around pairs of hyphens -- like so -- standing in for dashes. Their style guide is designed so that someone doing the newspaper typesetting can directly copy the typewritten manuscript over to the press without thinking about what kind of dash to use.

In fixed-width fonts, do you literally use an en dash (U+2013) or do you use hyphen-minus (U+002D)?

I use UTF‐8 except when I have reason to stick to ASCII. (One such situation is public mailing lists, where people’s misconfigured mail clients constantly butcher any non‐ASCII characters when replying.)