“in the case of Judaism and Chumash, Occam’s Razor dictates that G-d did not give over the Torah in its entirety to the Jewish people”
That isn’t just Occam’s Razor, such opinions are found in the Gemara and Rishonim. The statement in the introduction to the Artscroll Chumash that it is a unanimous opinion that every letter was dictated to Moshe by God is false and a distortion of Torah — in fact the Artscroll Chumash itself cites the opinion in the Gemara that the last seven verses were written by Yehoshua. But the additions they cite are quite minor, just a handful of verses. The link from such small additions to the Documentary Hypothesis is completely unsupported by anything in our tradition and anyone who justifies DH based on Ibn Ezra is out of line.
And in fact, regarding the rest of the Torah text, it is not possible to prove or disprove its age, or its Divine origin, and anyone who says otherwise is promoting junk science.
Let me give an example of a successful proof of authorship, which shows how these methodologies work, and also why no rigorous scientific statement can be made regarding the text of the Torah: The Federalist Papers (well worth a read) were published anonymously in 1788 to promote the ratification of the United States Constitution. We know that the three authors were Alexander Hamilton, James Madison, and John Jay. However, for some of the papers, whether they were written by Hamilton or Madison was uncertain. Modern scientific analyses comparing the papers of uncertain authorship to contemporary works by the two authors have shown pretty conclusively that the works of uncertain authorship were in fact written by Madison.
Compare this to the attempts to promote a late authorship for the Torah: There are no documents in the Hebrew language from the time of Matan Torah, and none other than the Prophetic works for many hundreds of years later. The only Hebrew language work available are small inscriptions found in archaeological sites. There is nothing with which to compare the Torah text! It must therefore be concluded that it is impossible to either prove or disprove the hypothesis that the text of the Torah was written in the time of Moshe Rabbeinu, and it must either be accepted (or rejected) on faith. It is not a falsifiable proposition and must remain non-falsifiable until such time that some archeologist discovers a huge trove of three thousand year old documents in Hebrew. It is unlikely that that will ever happen. The folks who insist that it has been conclusively proven that the Torah text was written later are simply out of line.
This does not mean that literary analysis, including grammatical structure and the study of the meaning of the many cognate words found in other languages to Hebrew can’t inform us on the meaning of pshat. Such is not a threat to any fundamental of Judaism and should not be treated as such.