Such a great question! You’re right—it is exactly a kabbalist’s job description.
I’ll answer (though not a kabbalist myself) with an example of Man. Man in Hebrew is adam. In our Yeshaya, 14:14, we find (in Hebrew) ADAM-EH L’ELYON, (I will be like the Most High)
ADAM-EH means “to be similar (to)” This is the basis of the etymology of Man being “in the image” of G-d. He created our existing spiritual and physical worlds with the Holy Tonge (Hebrew) and the Torah can only be understood, in plain meaning and in contextual meaning, with an understanding of Hebrew.
...if you remain unconvinced, I won’t be offended.
For graduate Jewish study, here is a chapter of Rabbi Shneur Zalman of Liadi, ZT’L, the innovater of the Lubavitch chassidic movement’s “Shar haYichud v’Emunah” (The Gates of Unity and Faith” talking about your question:
http://www.chabad.org/dailystudy/tanya.asp?tdate=6/5/2014
It’s hard to convey the meaning in a linked interlinear (with one language being illegible to the other party) website. If you really want to understand more PM me please.
IN BRIEF ANSWER TO YOUR LAST QUESTION-— (which Hebrew letter...) it was actually the words, the combination of the letters (each with its own energy) that counts.
I remain very much unconvinced. The apostle John, typical of enlightened Jews of the first century (the early church), had a much different interpretation of what "By the word of the Lord were the heavens made" (Psalms 33:6) meant. And it wasn't Hebrew letters!
In the prologue to his gospel he said, "All things were made by him; and without him was not anything made that was made," "And the Word was made flesh, and dwelt among us..."
The "Word" that created all things, in the fullness of time made flesh, and dwelt among us, was none other than the virgin born Jesus of Nazareth (Yeshua to you), your Messiah and Savior.
Why not take the insight of John and the rest of the early Jewish church about the meaning of the creative "Word?" Instead of the highly mystical opinions of Kabbalists? John and the early Jewish church, after all, were as much, if not more, Jewish than you, moreover, they lived some 2000 years closer to the truth than you.