Yes. Adjectives formed from verbs, adjectives, and adverbs should be linked together by a hyphen, as they jointly modify a noun. Otherwise it can make it difficult to see their meaning.
You hyphenate it only at the hyphen.
Can you, or should you? You can hyphenate it if you're moving between lines in a paragraph and need to break up the word. You shouldn't hyphenate it normally.
McCarthy should not be hyphenated.
not required
A hyphen is not required.
Yes it should be hyphenated.
Yes it should be hyphenated: co-worker.
Yes it should be hyphenated.
Yes, hyphenate by-laws.
According to the sources I've found on a quick search, you should hyphenate 'coauthor', i.e., it would better be: "co-author".
You do not need to hyphenate.
You do not hyphenate the number.