I think in this case you would be justified in using force (pepper spray, fists etc) because the guy had already assaulted you when he tried to run you off the road, etc., and he was threatening physical harm to you again when he got out of the car and came up to you. You have to make the split second decision to fight or not and if you do, hit first, hit as hard as you can and hit again until the guy is immobilised.

If you are going to pepper spray somebody, be ready to run, or finish it off, like Rule said, he is going to be pissed off. I do not agree with foible that you should let him hit you first. The first person to throw a punch usually wins.