Hi!
1.I've played the game hundreds of times while testing and found no problems with the daggers. You may create a map of the area so that you avoid going to the same place multiple times. Going around the root might help!
2.I don't like giving too many details about the game and spoil the experience for other players. This said, there might not be any other characters.
3.The max size is randomized at the start of each gameplay session with different numbers for AE/BE and is never the max size! Upon completing the game you may receive ways to unlock the max size.
Hope this helps!