Thats quite a bit of stuff!The majority of these issues have been fixed already but are not pushed through juuust yet.
Yes only one item, the sack is to make it so you don't have to make multiple trips several times as you can store as much as you want in it.
This isn't really explained very well just yet but putting other items on the button also opens it (you can also exit through the big open gate in the big round room)
I might look into moving the camera further away though. All stealth game are inherently puzzle games at it's core! The path you take is generally the solution to the level (puzzle)