No comments on Part 5
Part 6:
I see no way to fix the bookroom so I'm going to disable the gateway into that room and remove the hidden items
Floor 63 minigame should work just fine. I see no reason in the code why it wouldn't work. There are even 12 hidden items there. I even went and tested this by playing up all the way from before you storm shinra HQ.
Floor 66: I did not reference Dirge of Cerberus. Never played it and don't consider it canon.
Midgar Zolom: Stealing doesn't work because it has nothing to steal. I don't know why you think it has a Mega Lixir.
Floor 69: The vending machines are a minigame, try them out a little more, you can get a set of rewards for finishing this minigame. You know it's finished when the whole set of vending machines start to blink like Las Vegas.
Dying: There should be a save point after Rufus is defeated. Did I not upload that flevel? I changed this a while back when Sega first checked the Midgar bosses out
Part 7: No real comments, you could mention that the Junon Forest fights are among the best spot to level up early in the game