129 minutes is the number that was bandied about rather often post-release, as was the fact of Bennett cutting that version down after the Kansas test.
It's entirely possible that was a typo that got repeated, and that it was in fact 119 minutes, or that it WOULD have been 129 if you added the credits and the epilog -- those numbers certainly jive better with the relatively little extra material that has surfaced, all of which you reference above.
As near as I can tell, except for the new epilog, ILM's work was finished in April (it had to be, since they had to start printing reels WAY early in order to have 70mm prints done in time for June), so the runtime shouldn't have changed with respect to VFX shots, since the timings for the 'scene missing' cards would have matched to the projected VFX.
My understanding was that the reshoots did not take place long after the end of principal; if this is not correct (and your post certainly makes this inference), can you enhance on that end of things? Since he cut at night during shooting, the rough cut should have emerged within a couple weeks after the end of principal photography. And when you say the studio, are you referring to Bennett or somebody higher up?
The cut stuff to me sounds as it always has, like a mix of stuff that would have dragged with other stuff that would have helped and improved the film (and yeah, a longer version of a movie CAN feel shorter - apparently GODFATHER 2 tested with 45min cut and had walkouts galore from boredom.) I'd definitely want to see this cut for myself before commenting further.