From what I've read thus far, it looks like you are doing the compiling (correct me if I'm wrong!), and I wanted to ask if I could have a copy of what you've done thus far. I may prove helpful in the theory department: my first degree was in English, I'm working on one in Japanese, and I speak a smattering of French, German, Korean, and Latin. I've actually taken a course titled "History of the English Language," although it went back in its theory much further than the roots of English. I might be helpful for things like, "what sort of an ending would a word/sound have" or "why would you find a series of vowels and consonants in a certain order with such frequency," etc. I think this is a brilliant idea, and I'd love to help!
I definitely echo what I've read from others, in that I suspect the Elves that used Sending more than speaking are more likely to have a simplistic, more image/emotion based language. I do think that they must all have a common ancestor, however, much as the Romance Languages all do. ^-^