SBF... cool investigation. But I think you are missing the biggest point of it all. This very topic led me out of the witnesses... and turned me atheist.
Let's say JW's are right in this: The original NT had a form of the Divine Name in it, but later it was removed.
What does that say of the Bible?
Well, it shows that there is absolutely no way that anyone should ever trust the Bible.
Let's say JW's are wrong in this (impossible to do as it stands because it implies denying a negative), the original NT never had any form of the Divine Name in it. The LXX having forms of the Divine Name was just a historical oddity, but all copies past the 3rd century didn't have any form of the Divine Name.
It also shows that there is absolutely no way that anyone should ever trust the Bible.
The evidence you have shown up to this moment is that the early LXX and the late LXX are different in a very important respect: the Divine Name was removed from all copies.
THIS ALONE should be a huge red flag.
The best complete or close to complete copies of the LXX are in the same book as 3 of the best and oldest complete copies of the NT.
The Codex Sinaiticus, the Codex Vaticanus, and the Codex Alexandrinus all contain a copy of the complete Bible in Greek, and are from the 4th/5th centuries...
So they contain a corrupt (according to you) copy of the LXX and a complete copy of the NT.
They were in most likelyhood made by the same people. So if there is a doubt as to the "purity" of 2/3 of the entire text of these Bibles... then why think that the NT text wasn't corrupted in some other way (this applies both to YHWH being there originally or some other way)?
You just threw away the belief in the entire NT, as the Great Uncial Codices (there are 4, but the last one doesn't have the LXX) are our best and earliest copies of the NT.
That's one major point... I will make another in another post.