My offical response.
X-Buster charge: Release Y during the sequences where you can't control X. He'll keep charging. The moment (or very slightly before) you gain control, press Y. The window of opportunity is narrow, but wide enough that you should be able to pull it off on the console.
Elevator glitch. You know, I have no idea. I did it entirely by accident, and was ready to rerecord over it before I noticed what had happened. I couldn't even reproduce it on subsequent trials.
The dialog bug. You have to reach the gate without touching the ground.
Take a look at this. Also, try playing the movie and terminating playback in the anteroom and wait a moment.
Dash jumping over the floor. There's also a slight annoyance that jumping from a dash seems to stall me for a frame. Getting as much horizontal distance as possible makes me feel a bit better about doing that.
Boss Baiting
Not much I can say that would be useful here. Almost all bosses have an invlunerability period of exactly 60 frames. Chill Penguin seems to have 70 when I blasted him with the X-Buster. Vile has 25 and Velguarder has 24.
The only comment about the AI I can make is the Bospider may be provoked to drop spiders while moving if you jump while it moves. Everything else which seems to be random probably is.