The Siegelsbach nuclear missile facility is actually a closed US military depot that used to store nuclear weapons (as well as other munitions) although it wasn't actually a launch facility (in the film it's referred to as a nuclear facility or a nuclear base).
The scene in the parking lot where Elwood is tasking Knoll with getting the food for the big cook, was filmed in the parking lot of the US Army Karlsruhe Shopping Center, part of Smiley Barracks and Paul Revere Village housing complex, which had been recently turned back over to the Germans at the time of filming. Directly behind them can be seen the base theater "Minute Man Theater" and while the shot pans around to reveal them entering a building marked "Commissary", this had actually been the base PX at the time, with the Commissary located in a more confined area.
Elwood disables the girl's car by disconnecting the battery
link, but when she tries to start it you can hear the car turn over. If the battery was disconnected there would have been no response from the engine at all.
When Sgt. Lee and his daughter in the car after the Civil War party, she asks him if he wants to kill Elwood, to which he asks her what she's talking about. She says, "Do you?" However, her lips do not move when saying that line.
When Elwood is seen lying by the side of the pool having been beaten up, he is surrounded by splotches of his own blood. These vanish shortly afterwards.