This is fantastic--both the frame story and the ambiguity of the letters themselves, since you point out in the very beginning that Merry might not be putting all he feels into the final drafts. I love this picture of him, never quite reconciling the two worlds he lives in, his lingering grief for Frodo, and the life that he builds for himself in spite of that.

And AHAHA, after having read a lot of historical letters myself, the bit about the missing barrels of mead is TOO REAL.