Seems like you're having a lot of trouble! How often do you need to restart your Macbook? Many users that I know seldom turn them off, so the boot chime isn't a common issue. You could choose to not shut your MacBookPro off.
I'm not sure about the MBP - does the volume of the boot chime vary if you set the main system volume to different levels? I would expect not, if muting doesn't turn the boot chime off.