Well spotted on the ceiling height differences, I can't believe I never saw that!
Regarding the corridor measurement, that 64' wouldn't be a reference to RADIUS TO RADIAL BEAM 64'9"
That distance actually refers to the midway beam inside the briefing room and is backed up by the numerous other measurements and 8' panels listed on the same drawing:
Using that 64'9" line as a scale, I deduced that the radius of the corridor was 50'3" and the radius to the inner briefing room wall was 52'7. Since I brought Cary up, it's worth mentioning that this is where I think he made an error in his reconstructed measurements. He stated that he the measurement to the inner wall was 55'7" but this is incompatible with the 63'9" and other measurements on that page.
Having said all that - maybe this is not the reason you picked 64' after all! In which case, carry on.