About 9:
So basically, your audio source for the music is not centered to the camera, but is just placed probably at (0, 0). This makes the music quieter when you get far away from (0, 0) and it also messes with the panning of it (how left/right the sound is) based on which side of the source you are. You can either attach the music source to your player/camera, or you copy the highlighted values from the image I sent.
Also, just to clarify, I still had fun playing your game, but in my feedback I always point out the things that I feel that it should be changed.
That probably makes it sound like I was having a bad time, when in reality it's just a cool game with some issues.