The last part was hard. How I beat it is I got out the left arrow to block the bottom ball so I could think, then when I figured it out I moved the key a bit to the left then jumped on it, dodging the balls then moved it up, then repeat until I reached the top and retrieved left arrow and used up arrow to walk across and retrieved it.
I was gonna make a new comment for this but merged it. Anyway, I thought the interpretation of the theme was, so if you moved a key into the world, that key would now be, "out of control". However, I looked at the description and it said it's actually make your path "out of control"s.
Before I even played the game (when I was watching the game jam video) I did/thought of a strategy: When you're using the keys as your path, always use only keys you're not using.