Separate question: has Pull of the Abyss ever worked on Despair demons?
It should. I know I used it recently on some of the rifts in Jaws, and the despair demons would go twirling in the air but not be able to fly out (they just kept getting drawn in).
Maybe there's a difference when you try to pull higher-level enemies (or those guys are just extra try-hard)?
I just confirmed that if you already looted that room before the patch, you get only the power amulet, no do-overs. 
Yeah, chests marked as looted can't be opened, even if the contents change.
A post-game or in-progress save isn't going to be able to get any of the new items (unless it's a chest you never emptied or enemy you never killed).
Yay, you DO get to loot Amulets of Power for the Inquisitor again.
That amulet was already there (they created that new container for it in Patch 5). It's one of the three lootable amulets that were left in the game.
Now that they've added an item, though, it's probably subject to the exploit they were trying to fix in the first place (since you can grab the power amulet, reset the area, and have another one spawn in). (Not that it even matters anymore with the storage chest duping.)