Someone can correct me if I'm wrong, but I beleive the Regex Validator does not validate on empty text--so you actually need an empty field validator as well.
With regards to your regex, I'm not sure how to catch it w/ 1 validator, but you could try breaking it up into two. 1 to test the overall length, and 2 to text the pattern.
Remember that . matches any character, including \r and \n. To match any character excep those, use [^\r\n].
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