Jack Welsh's book about the medical histories of Confederate generals states Tyler was placed in command of the post at West Point in January 1865; see page 219. Also W. J. Slatter (apparently the same person Tyler wrote to in the letter you have found) wrote in Confederate Veteran magazine in 1896 (see page 381-382) about Tyler and West Point. In a brief summary of Tyler's career Slatter did not mention any sort of temporary command of Bate's Division.

All this being said, I would love to see a copy of the letter. If you could provide a copy, just let me know.