At 3000rpm, you can hear the beginning of the vibrations and it seems to progress louder right through to 8000rpm.
Did you check the pulleys for balance?
If the motor is quiet on its own, I would guess adding anything to it( like a pulley), will more than likely be the cause of the vibration.
After listening to your video again(with headphones this time), there is little to no frequency squeal. It could very well be the belt and as you said,and that should quiet down once the cover plates are in place.
Either way, good job and congrats on your bachelors. With all the work you've done here it shows you are of caliber.