There should be no question. If you’re about to be carjacked, you have the right to defend yourself.
Castle Law aside, if an unknown person attempted to enter a car I was in they would also end up viewing the business end of my gun.
I fail to see what he did wrong here?
Must one wait until they are under attack to draw their weapon?
Seriously, how do your retreat from the inside of a car, other thank gun the gas if you’re the driver. And then you’ll hit the offender with your fender.