Thank you for your comments, david! Glad you're enjoying the game.
The reason why you can get some items repeatedly is becauseIf not for that, the game could end up with a dead end. Admittedly, there probably exists a more elegant way of solving this problem, but I'm far from being the world's best programmer. 
As for the character's slow movement, that was done on purpose but if it's too much of an issue it's easy enough to change it in an updated release.
The reason why you can get some items repeatedly is because
Spoiler
some of them are needed for two very different puzzles.
[close]

As for the character's slow movement, that was done on purpose but if it's too much of an issue it's easy enough to change it in an updated release.