I have progress but it's not quite right, yet. I often miss the really obvious. Case in point, I've been using your Javokis' walkthrough since day 1 every time I got stuck - about a month now I've been referring to it. I just noticed it was "by Rainmoon" today.

That being said, here's what I did:
Backed everything up, just in case.
Created a new NXT file in my strings folder.
Copied an existing one for the tags - which I could actually understand so I was okay with that.
Saved.
Opened my chronicle NMF file and added the line to include my new NTX file
Created a new item off Sir Cuthbert's letter in NOT editor.
.... crashed several times trying to spawn it....
Created a complete duplicate of Cut's letter except I renamed it CuthbertsLetter2
Stopped crashing and spawned it (obviously had a problem somewhere with what I was doing in the NOT editor)
It "spoke" just like the original.
Altered the ITEM_TEXT tag to mine
It didn't crash, but also didn't do anything except give me the sound effect for using a scroll or a book.
Curious, I copied the entire NXT file and placed it in my new creation. Saved.
Altered the original NMF file to only read my creation and not the original.
All letters spawned just fine, but none of them actually opened and said anything.
Restored the NFM file to original state.
Double checked to make sure I didn't give my game a nervous breakdown with my alterations, and was happy to find out I didn't... this time.
I do have progress since the item is actually spawning, but I'm thinking I must have a problem in my NXT file. Which is odd since it looks really straight forward even to me. I'm going to take a look at it again after work tomorrow, but if anything in my little path of Malkov up there is glaring out that I did wrong, by all means, let me know.