Thank you very much for the detailed response!
1) No, I don't have checkpoints, but I don't like that part of the level, I will redo it (for the 4th time).
2) Yes, looks strange, will be "fixed".
3) At 2:33-2:36 you can see that the rotation affects the movement and the jumping distance. They are rotating slowly because it's only the second level.
The levels contain some spots where the challenge is reduced (here f.i. 2:50-2:56). I think it's important to give the player some time where he can just run through the level without being in great danger.
4) Haha you probably know that it's the ghost from your previous best time? I have a level where you are hunted by a dark/ red glowing copy of Superku that mimics every move you make, though:


I think the controls are very good, just two buttons (you could even play the game on an USB NES controller), easy to learn, hard to master. And that's the motto of the whole game, I highly doubt that anybody who wants to finish the game will be able to complete it as it becomes so difficult.