If that was really what happened then perhaps you should have been a bit more specific in your apology, instead of just saying "I'm really sorry Sir" and not trying to persuade him that it was an accident and saying something like "I midjudged the distance Sir, i apologize" so perhaps that's why he got even more angry with you, not that I'm justifying his act, if it really was him who keyed your car afterwards then he really shouldn't have done it, no excuse, but perhaps you were not very tactful with him? don't know, i guess it's difficult to explain a dialogue of this by writing it down.

There are things out of place on his part like saying your car is a piece of shit and all that, don't know what seven series BMW were you refering to but if it was the one from the nineties it probably was as old as your car

As for the insurance thing I cannot help you in any way i guess, not sure how your policy works.

But i guess you feel yourself impotent, it's what happens in these situations in where something happens and we cannot do anything to avoid it because we didn't see it happen or simply we were just not able to do anything, so let's hope it doesn't happen to you again.