Thanks for your post, prometheus. I read it initially and have been further clarifying my thoughts and questions, and now I have read it again and I see it a little differently than before (it's funny how that happens !).
Firstly, I am definitely not "adopting" anything, per se, but simply organizing my mind. There were certain elements to my understanding of tone that were somehow (luckily ?) established when I was extremely young and was just working at the instrument all on my own. These days for me invovle large quantities of going back in time, so-to-speak, and organizing many aspects of my musical upbringing (which was nearly entirely without a teacher until my 20's). So, for me, this is not a matter of trying some kind of conceptual clothing on to see how it fits, exactly, but rather a case of finally finding some kind of order and organization for very deep experiences, in a way where I can hopefully much better call upon and use certain informations that I had in what seems like another lifetime. For me, it is a very strong sense of coming home.
Each of your points helps me further clarify my thoughts, but overall I realize that most of what I think you are saying is based in a form of tonal relativity, which is what I am currently thinking of as "moveable Do." Moveable Do is "all about" the experience of tonic and dominant and how each tone wishes to resolve to what we call tonic. This, I don't argue with and can now more plainly "see".
What I am thinking of in terms of fixed Do is a bigger concept, though something which envelopes the experience of relative Do (etc.). There is a much different kind of Tonic, for example, involved with it in a way that I can't currently put my finger on, exactly. I can say though that as a child, I could inwardly feel these pitches and movements away from and towards others, I could feel intervals -- they were more than sounds and pitches, it was something much, much more, and I specifically remember so much of that "revolved" around C (and I don't think this is simply because that's what I was originally "shown" by my Mom).
So, where this leaves me right now is that I am just working to better understand pitch itself. Yes, I 'get' that there are overtones and such. I 'get' that a single tone is not exactly what it seems. Actually, that is part of why I am continuing to dig -- there just must be some kind of basic value or basic concept that I just don't have words for yet.
I was reading a theory book just moments ago, even going back to the beginning where it is "explaining" pitch and such, and it gave a little historical background to some of the concepts. I found something which I didn't know in that, apparently, from about 800-1430 and in the Renaissance (roughly 1430-1600), musical relationships were understood in hexachords in a standard pattern of W-W-H-W-W, and apparently (?) first started on C. Apparently the first ever accidental came as a result of wanting to allow the hexachord to start on F instead of C, and then what followed was a hexachord beginning on G. Firstly, this is crazily significant to me -- as in it causes everything within me to sound all alarms ! But, secondly, there is SO much that is unexplained in that and which is being taken for granted (because there are parameters to the book and most people probably don't want to know what I want to know about it).
I finally started being able to articulate my questions. Aside from the fact that these early hexachords reflect the tonal movements from I, IV, V (as we could think of it today), they also called the hexachord built on C the "natural" hexachord, the one built on F the "soft" hexachord, and the one built on G the "hard" hexachord. That may not seem like much, but WHY do they name them like that, and also, WHY did they ever start with C, and WHAT was the natural flow which led them from there to the IV and V ? And, even beyond that, I was finally able to articulate my deepest question regarding tone itself.
How did a "single" tone every become distinguished in the first place ? To me, it seems that all tones are actually some form of being indistguished as individual tones. This is not as reflected on something like the piano, because we visually see that each tone has an individual key and it is very easy to take that at surface level. But, on something like the violin, for example, or in singing, where pitch can audibly "bend" and all of the distance "between pitches" can be explored in greater depth, I think illustrates part of where my questions currently lay.
To me, it's as though tone exists as one great sound (though it's more than sound) -- as though there is just this huge bog of mud. How did somebody originally EVER distinguish that there was in fact a grain of sand (or so) within that bog of mud ? I don't get that. How did we ever decide that the whole bog of mud was in fact made of individuals particals ? AND, what made somebody distinguish C first ? What in the freaky french fry does it represent

Now I'm angry ... haha. I need to go practice and calm myself down.