Very well written. You presented your predicaments in an orderly fashion, and I have no problems understanding how you found yourself from A to B to C.
Not knowing the layout of the parking lot, I think that I would have tried to have more distance to the situation so that the BGs weren't "challenged" by your intrusion. They have big "personal space" when it comes to someone ????ing up their agenda.
If you had been a voice shouting "Hey, you coming?" 30 yards away from behind some headlights, do you think they would have responded differently? At least it would have been a more elaborate and less cool sneak-up by the guy wrestling with your car window.
And of course the call to the police. However, it is a wicked to say exactly when you should have called them. I don't think you get much priority when you are just "concerned", especially at the time when the night clubs close. Just like you leaving them in the bar... you are never sure wether you are in one of the unlucky cases that actually will turn ugly until it actually turns ugly.
I think it is pretty drastic to say that you don't want to go out with those girls anymore. You should give them an earful, sure, and that they should take your advice next time. And, of course, that they agree that this was sheer stupidity rather than "we have guys who will save us".