What LCD is used in the Pixl.js? Datasheet? OSHW?

Did you notice a difference between standby/sleep with your discovery board? I guess you could always just use a decent size capacitor on Pixl.js to even out any peaks in power draw?

RTC function surviving to resets and code uploads

It should survive code uploads and software reset? A hardware reset is tricky though - there's no backed up RAM on chip as far as I know, and no separate domain for the RTC so it's hard to work around. If all you care about is restoring time you could always do something like:

var uploadTime = getTime();
function onInit() {
  setTime(uploadTime);
}