Pronouns

Standing in without confusion.

Who and whom

Who is the subject and whom is the object. Answer the question with he or him: if him fits, whom is right, which is the test that survives every complicated sentence.

Between you and me is correct, because a preposition takes the object form.
They as a singular pronoun has been standard English for centuries.

Clear reference

A pronoun should point at one obvious noun. If a sentence has two candidates, repeat the noun rather than making the reader guess.