Nope, --my-- engine has TWO keys just the outer one was badly damaged. I have used the woodfruff key from (single key type) spare engines crank which fitted tightly and is slightly longer top extensions. The outer key was very badly damaged by the pulley spinning. (The photo shows the empty keyway and was taken after I extracted the damaged woodruff key)
I suspect this specific weakness (single central bolt/small short key into the pulley) is the reason they changed to twin keys when the extra loading of air-con, higher amperage alternators and new pumps were added.
As for the misfire, that remains to be seen, I will run the car up to temp/investigate with the Aux-belt removed. I can use the damaged damper to prevent the belt coming off the timing cog as there will be no loading on it.