The Encyclopedia entry Viktor reads lists Sissy's death on October 1, 1989, the same day of all the Hargreeves's births.
Klaus running away from the Amish over the hill to the car yelling is a reference to Indiana Jones and the lost Ark, where Indiana runs from the tribesmen running to the plane.
The car is a Toyota Crown.
Klaus and Five are in a car, with Klaus driving them to Pennsylvania. They are in the United States, obviously, but the driver's seat is on the right side of the car rather than on the left side of the car.