My question is about "Ms". I wonder what the period is for? In 'British English', as opposed to 'American English', if the abbreviation ends in the same letter as the word there is no period. But under no known variant of English, that I know of, is there a period after a word just because it is very short and lacks a vowel unless the word is a contraction/abbreviation.
As EA wisely points out, punctuation incorporates a degree of arbitrariness, so the answer will depend on the style guide you choose (or the one chosen for you). If it's any comfort, The Chicago Manual of Style places a period after Ms. and includes it as an abbreviation. Your unease may arise from the fact that Ms. is not an abbreviation for any honorific in the way that Mr. is short for mister. But that doesn't bother the editors at CMS, so you shouldn't worry either.