I do enjoy reading what you big plane flyers write.
The nature of a flat spin is that recovery via unsustained flight control inputs is highly unlikely and, because of that high centrifugal force, anything not tied down in the cabin or holds would've migrated aft, further exacerbating the aft CofG complication for a flat spin.
On this particular point, I do believe that it's a standard spin where the centrifugal forces would migrate everything aft. In a flat-spin they go to the nearest extremity, what's in the cockpit gets forced forward.
takata
Again, it is mostly your imagination: what clue do we have for considering the aircraft 'deceased' at 0214?
On this point I'm with JD given: the preliminary report of essentially vertical impact on the belly, the projected positions at 0214 being in the neighborhood of the initial debris finds, and the most likely reason a satellite connection was lost. They tend to pair up. All other possibilities get more complex.