There are several quite in-focus and clear video frames which show both the shuttle, a large, star-shaped hole in it's underside 2/3s back, left of center, and the tail spinning off to the right, with the black rudder lines visible on it.
My take:
-L wing heats up from thermal tile damage.
-The L main landing gear gets too hot and explodes over CA, reigning debris.
-The explosion cuts power and telemetry in the shuttle, crippling it.
-The force of the explosion (L side) rolls, then yaws the shuttle to the right.
-The shuttle continues its descent, now facing almost due South, sideways to it's glide path, without power.
-3 Min.s later it crosses over Texas and is captured on amateur video, facing South, large hole center-left 2/3rds back, without a tail and in several frames the tail can clearly be seen tumbling away to the right. In at least one frame even the tail's black rudder lines are visible.
-Travelling down it's glide path facing sideways it burns and breaks-up beginning over the Dallas area. The video in effect shows this at it's conclusion.
Keep in mind the video shot from Dallas is 3 min.s after telemetry was lost from the shuttle @ 207,000 and 12,500mph. Instead of 36 mi.s it would likely have been 20 or so miles high when it passed over the Dallas area. The video shot is by no means improbable. If I can make out the tops of water towers at 30mi.s across Nantucket sound on a good day I think the shuttle at 20 mi.s in altitude is even more probable given the fact the observer was at 1,000' alt. and it was a clear, dry and calm day.