Is the 4K version on iTunes the same as the one on Amazon Prime?
Yes.
Quick update for everyone - another user is taking over this project. I won’t share his details here, as he has not cleared me to do so (I haven’t asked yet). Basically, the project proved to be a bit over my head, so this user has graciously offered to take over. As a result, it is delayed a bit further, but I am mailing him a hard drive with all the requisite files, and he will be syncing the project to the Blu-ray audio, the LaserDisc audio, and the original Cinema DTS audio.