Great and interesting visualizations!
But I really do suggest you double-check the first frames of the scene in TWOK where Kirk "slides" down the engine room ladder. There is something noticably odd with the wall structure on the upper level, hinting a starboard stern door on the upper level, IMHO.
Update: The first frames of the scene with Spock descending the ladder clearly reveal the starboard door leading astern on the upper level.
If I'm not mistaken, Kirk's entering through that door in TMP (to arrive at the upper level) would be more "natural" and we wouldn't have to worry about the TWOK bulkhead door at all.
Regarding the width of the connecting dorsal pylon I had previously relied on the accuracy of the Kimble blueprints.
However, the actual VFX model of the TMP Enterprise
reveals that the maximal width of the dorsal is 59% of the maximal width of the torpedo bay section (which is wider than the Kimble blueprints suggest). According to my calculations the max. width of the dorsal on a 355 m O.L. Enterprise would turn out to be 8.4 meters (and not the 6.3 m I calculated previously, based on the inaccuracy in the blueprints).