LMMS is awesome, I make all my music on it. I do understand not having time to do more music, and it's impressive that you managed to make quality assets for all aspects of the game on the short time frame.
About the controls, I find it challenging to point specifically what exactly makes a platformer feel good or bad. At my first comment I had the impression that there was a input delay for the jumping, but after playing it again, I'm not sure anymore. Maybe it's just the lack of classic platformer responsiveness features, like coyote time and jump buffering.