Marhwini, I think there are couple things about your pursuit of a Unified Theory that are ruffling our collective feathers, and it seems to me worth it to pursue them:
1. Tolkien's work is
art. There are things within his books that take place not because it fits within a specific physics or metaphysics, but because it is
artistically appropriate. The sciences most appropriate for analysing
The Lord of the Rings is and will remain aesthetics, form criticism, or philology.
Tolkien definitely aimed for verisimilitude--most writers do and especially those writers who say things like "I cordially dislike allegory in all its manifestations, and always have done so since I grew old and wary enough to detect its presence. I much prefer history – true or feigned– with its varied applicability to the thought and experience of readers." I certainly agree that thought was put into the "behind the scenes" mechanics of Middle-earth. Where I disagree is in thinking that these can be definitively revealed.
Perhaps the most apparent way of stating this part of the problem has already been made by
Morthoron: how do you reconcile a Talking Purse in the Possession of Trolls to your Unified Theory?
2. And a major part of the reason for this is that Tolkien
changed his mind about things! Middle-earth only exists or has a definitive form insofar as he gave it one. It's one thing for Tolkien to decide that a certain metaphysic must apply--if anything contradicted it, he was able to change it. But for the rest of us who can only study matter, what are we to do when there are competing traditions? Was Arda flat at one point? What is the nature of the stars that Varda made?
Tolkien had the freedom to reject concepts AND to completely modify texts to fit new theories. We see this especially with his linguistics (since, of course, this was the field he was most interested in), but we also see that he had a profound respect for anything that he'd already published: note how he dropped the whole "problem of -ros." And, of course, he'd forget he decided something now and again without specifically writing out that he'd done so, so you're looking at a dubious metric in using "whatever his latest opinion was."
Basically, you can't have a Unified Theory without first establishing which texts are permissible to admit as evidence, and you can't do that unless you first establish what is canon.
It may be somewhat ancient history now, but we on the Downs have fought many wars over Canonicity before (
here is but one major example), and you first need to demonstrate there is a clear, unmistakable canon before you can start deriving anything approaching definitive conclusions.
To be perfectly clear, I *like* the idea of exploring some of the metaphysical or physical ramifications of Arda-as-Revealed, but it always has to be approached with the same sort of attitude as approaching a contrafactual question like "what if Melitot Brandybuck found the One Ring?": you can base it on evidence, make a clear and compelling case, but you cannot PROVE it.