You propose an alternate explanation for the start of the universe, and name it the Big Spill. If I were less of a scientist, the name itself would have me reject your idea out of hand, as a spill is a mess to be cleaned up, while a bang is a loud noise, indicating something impressive has just occurred. Spill = Housework, Bang = Party. But moving along:
Your statement that “…Studies on CMB radiation… still call for more observational validation…” is valid, and being acted upon. The Planck spacecraft is looking into it, for example. Note: CMB (cosmic microwave background) radiation is held up as radiation left over from an early stage in the development of the universe, and its discovery is considered a landmark test of the Big Bang model of the universe.
It’s like a photo of my dad’s cigar butts, empty beer cans, and open cowboy novel in the family room; not a picture of the thing itself, but you get a good idea of what was there.
Before we drink a Big Bhang lassi and float down the river of speculation about the mechanics and physical starting point of our universe, let us instead consider the more important, more interesting, and unanswerable question that you bring up: Where does the BB material-creating "...ultimate system of all creations..." come from? Passing it off as "pure energy" or "other-dimensional" is intellectually naughty, Jethin.
Where did the very, very first bit of physical stuff come from? One must choose the unsatisfying, but rational answer, “I dunno”, or the comforting but untestable response, “God”. Let’s split the difference, and agree that no-one knows yet, except maybe God(s), but he/she/they have been pretty quiet on the subject.