‘I should add, aside from these points, Rashi surely had a more authoritive version of Seder HaOlam — closer to its authorship than us — despite any so-called “modern research” (a/k/a rubbish).’
This is not “modern research” or “rubbish”. There are sources mentioned here that agree with the other texts of Seder Olam Rabbah. See for example are Tosafot to BT Yevamot 61b. There are many places where we know Rashi had a different text of the gemara than we do today; somehow texts got changed in the transit between Eretz Yisrael or Bavel and France. We should not force a single midrashic interpretation as the *only* one when there are others that have support from our mesorah.