Does anyone know where I can find an exhaustive list showing how each alphanumeric and symbol character sorts in Calc?
For example, in ascending order, does “=” (equal sign) come before or after “–” (en dash)? I’m sure there must be such a list but I can’t find any.
I doubt there is such an exhaustive list (at least easily parsable), taking into account that sorting follows Unicode collation rules, takes into account the locale of the data. This might be the starting point … maybe @erAck has better links 
That ICU collation documentation is pretty much the best you can get… some links to details and collation charts also in my collation bookmarks.
For that specific example, – U+2013 before = U+003D (but you can always try sorting in Calc and you’ll find out), and all dash characters after - U+002D hyphen-minus.
Note that there is no “the one exhaustive list” because collation/sorting depends on language. You could sort by Unicode characters’ code points (like in old ASCII and code page times) but that’s not how it’s done. See some links to details and charts in my collation bookmarks collection.