what about typos? are they words, or merely (mis)representations of words?

You might want to count them as word variants. So, is a spoken word less of a representation than a written word? How does one misreepresent a word? In a court of semantics? Luckily we have a lot of inherent redundancy in English words, so an a mistakenly wrought for an e has little impact meaningwise, but humor, ah, that's another thing.