Don't worry, this is all valuable criticism to me, especially since I will be submitting this to a contest soon!
Ohhh, I see, you fell through the map... I've been trying to recreate that bug for ages now, but it just won't show itself, lol.
Regarding the health, the way it works is that you only start with 50% health if you entered the checkpoint below 50% health - if you had above that, you start with whatever health you had touching it. It was designed that way because I thought it would at least be better than potentially restarting with 1% health, and didn't realize what problems that would cause. But it's noted now.
About maintaining speed on landing, you can let go of the analog stick before landing to almost instantly cancel your momentum. There is actually a hint in one of the rooms right after you get the scythe telling you this. Noted, though!