Just followed a link to this thread from an ex-JW blog. Great research, very informative. A couple of minor points I'd like to make:
1) The Greek word idou "behold!" in Jude 14 is of course a verb so it cannot be vocative, which is a case pertaining to nouns and adjectives. I believe you meant to say it's an imperative.
2) I think that the term "seventh from Adam" would naturally include Adam, in which case Enoch would indeed be the 7th rather than the 6th of the line. I've seen this sort of reckoning of ordinal numbers quite a bit in classical literature.