Take two or three pictures until the RAW histogram ETTR hint is less than 0.2j
Turn on raw histogram in the overlay menu, make sure image review is not turned off in Canon menu. Take a picture. You will see a histogram and there will be a number on it. This is how many EVs you can increase the exposure until overexposure. Alternatively, simply turn AutoETTR to "always on" and take pictures until you only hear 1 beep after a photo (2 beeps means you need to take another photo, 3 beeps means exposure limits have been reached=>proper exposure is impossible with current settings).
AutoETTR will change the exposure for you, that's the whole point.
#1. If you have a wider lens, use that instead. 50 is not that great for timelapse.
#2. I would leave WB on auto (you can always change it in post, might as well have a camera reading for reference)
#5. I would open the aperture up (for when it gets dark later on), say maybe at least f/4
#11. I wouldn't put a "stop after", what if something awesome happened right at the end of you sequence? You'd miss it. Just stop the timelapse when you're ready to stop it. Also, like barepixels said, your intervalometer period needs to be larger than slower shutter setting.
#12. If you have Adobe Bridge, consider using
my script instead of doing in camera deflicker (deflicker takes some time to run and means you will need more time between slowest shutter and interval, usually 5-10 seconds to be safe). It's basically the same algorithm, but doing it in post is so much easier.
