Hyphens, En Dashes, Em Dashes

Q. In your hyphenation table (CMOS 7.89), why is “mid-twentieth” in “mid-twentieth century” hyphenated? Shouldn’t it be closed up as “midtwentieth century” or have an en dash instead of a hyphen?

Q. Do you recommend using en dashes and em dashes in tweets? Or hyphens?

Q. What is correct style: “X and Y axes” or “X- and Y-axes”?

Q. What combination of hyphens or en dashes is used to punctuate “a four hundred year old shipwreck”?

Q. Hello, No hyphen after a number and before the word “percent”; that’s the rule, per Chicago. But if part of a longer modifier, would the following be correct? Mike said, “A 15-to-20-percent-a-year increase in sales is what’s expected.” Thank you.

Q. I’ve been having a discussion about the use of the term “water-resistant.” Chicago style dictates the use of a hyphen in such a compound only when it precedes a noun. However, the term is recognized by Merriam-Webster.

Q. Does CMOS have an official position on hyphenating “the then” when used to indicate something or someone’s former status?

Q. How would you treat “over apologize” in this sentence? “Be careful not to over apologize.”

Q. Hi CMOS—I work in mortgages, and with the increasing popularity of a “digital lending process” come electronic signatures. No one in my company can seem to agree on how to style this particular term, and as you can imagine, it comes up quite a lot. I’ve seen it four ways:

e-sign(ature)
E-sign(ature)
e-Sign(ature)
eSign(ature)

As I’m working on our in-house style guide, I’m also having to decide how it’s styled in a title or section heading of a policy document. Currently, I have eSignature as a noun and e-sign as a verb, and when it’s a verb capitalized in a title or section heading, it’s E-sign. I need to decide on four styles: (1) noun in a sentence, (2) noun in a title or at the beginning of a sentence, (3) verb in a sentence, and (4) verb in a title or at the beginning of a sentence. This is making my eyes cross. Am I good with what I have, or do you have a suggestion? I’ve consulted M-W and turned up nothing.

Q. Is word-for-word hyphenated? Is side-by-side hyphenated?