Other than having to reset the starting point (which was addressed) and some glitch that occurred that probably won't happen regularly, this level is fairly solid. It's basically what I want "Crystal Islands" to be: introduces a new gimmick in SMBX and then exploits it ala DKC style. My only gripe is the surprise difficulty curve at the end, but you mentioned it in your video so I won't hold it against you. That and I think a couple enemies were annoyingly placed (bouncing slimes on an upwards slope, a parakoopa floating between a tight passage with spikes).
The level looks great, and the music fits perfectly (I'm assuming you made it yourself?). It reminds me a bit of this track
from Super Mario 64.