I bet that was a fun ride, next time you're tightening that bolt get the rear tire on the ground, pull the rear brake, put your chest on the seat to hold the back of the bike Down, then tighten it with all your might. I've yet to ever break or strip a primary shaft from over torquing.
Also cut the area around the clutch housing on the cover so you can see the whole clutch. Just take an angle grinder and make the raised circular hump for the clutch flush.