Although Nibley has a great sense of humor, and is extremely well-read in a number of languages, when he starts talking about proof for Mormon scripture he uses shoddy scholarship.
To understand Nibley's approach to scholarship, see:
Salmon, Douglas F. "Parallelomania and the Study of Latter-day Scripture: Confirmation, Coincidence, or the Collective Subconscious? Dialogue: A Journal of Mormon Thought 33, no. 2 (Summer 2000): 129-156.
For the faithful Mormon, this book has some excellent quotes.