What’s the original pronunciation of Biblical Hebrew, and how do we know?

Linguists, historians, kabbalists and almost all rabbis agree that the Yemenite pronunciation is the most accurate and original, for: 1. They didn’t move around and were less prone to outside influence, compared to Jews in the other exiles. 2. Hebrew is obviously similar to the other Semitic languages, and the Yemenite is most similar to Arabic and other Semitic enunciations. 3. The Yemenites have a different sound for every single letter (pretty logical!), even a variant sound for every letter with a dagesh, as opposed to the Ashkenazim who illogically say "alef" like "ayin", and “tav” without a dagesh like “samech”, or Moroccans who pronounce it like “tet”, and both say “caf” with a dagesh like “kuf”, and "bet" without a dagesh like "vav", etc. Why would God (Who created Hebrew) have so many letters for the same sound?! 4. The Zohar goes into precise detail and explanation how the mouth, teeth, lips and throat pronounce each letter and it is clearly the Yemenite way. This doesn’t mean that everyone has to start saying Kriyat Shma or Parshat Zachor like the Yemenites, for everyone can follow their family or local custom which has been accepted. [Please see the previous question and answer]