Just changed a belt on my 2006/650. Although some people claim that it's easy to change the belt without removing the primary, I never had much luck at it. Perhaps if you HAD to, you could make it work.
Like yourself, my first attempt at removing the primary using only a wrench didn't go far. I've got my Father's day list submitted already....IMPACT WRENCH. You'll be surprised how easy it is with an impact. You may need to throw some heat on the nut as it is installed (and reinstalled...don't forget) with red loctite.
Regarding the burning rubber smell and the issue with changing between gears. That's the exact same symptoms that I had about 30 minutes before the belt snapped and left my son and daughter stranded and calling for a tow (at 1 in the morning). I wouldn't worry too much about a small chip off the primary, as long as it didn't damage the main hub.