Jerry since that crank seal popped out should I replace it instead of just pushing it back in like I did?

I would replace it just to be safe.  The sheared key probably caused the engine to backfire because the timing was way off and blew the crank seal out of the case.  The seal on the clutch side may also be blown out of the case.  A backfire sometimes breaks the reeds.  Check your reeds for damage.