Final update?
Today I built the first release candidate. I did a play-through and all is good, so the version is now with the testers (that have been doing an amazing job, btw).
I have 289 bytes left for bugfixes (hah!), and I managed to squeeze in three songs (plus intro, menu, game over and end game).
I'm exhausted and looking forward to release the game. If the testers are happy with this build, it'll be the one I'm using as master for the physical release and the free download.
So close!