Put a piece of clear packing tape over it to protect it from water getting in and you'll be fine short tern until you get it fixed. I'm assuming if it's 'plastic' that it's some sort of Saturn vehicle?
We have plenty of packing tape hanging about, given that we are moving next week; yes it's a Saturn so it is made of plastic, which in a way is a saving grace and I can probably buy the door panel and install it myself, it's only held on by hex screws.
As far as the guy claiming it's your wife's fault, he clearly hit it in the middle of the vehicle not at the ends, so that blows his argument. You can't go after his car insurance but you could file take him to small claims court for the damages. (probably not worth the time you'll have to put into it) to get him to pay for the 400 bucks or so to patch and respray the door.
I don't need the additional hassle of legal cases at this time; and it was a her, not a him... accidents happen but trying to shift the blame is unacceptable, personally if I was responsible, I'd first of all apologize then offer to pay for the damage; but it seems that not many people have any honour these days!
My Dad had something like this,It was a green Rover 618i (I think)I choose the colour(green) and we got it,4years later,a drunk dude was doing 50 in a 30 zone,Rear-ended him,then cut him off,Bonnet crumpled and rear bumper gone,the car was written off,I miss it so much
Our previous car was written off two years ago by a driver who was on a cell phone and rear ended us at a stop sign. He claimed brake failure, and the police didn't investigate that either!