Audio problem: While Lynda is filing her nails just as Michael enters the scene wearing a sheet and glasses, the sound of her filing continues despite her pausing.
Audio problem: When Laurie's crying near the end her mouth isn't moving in sync with the audio.
Answer: There are only two families that hire babysitters in the film, the Doyle and Wallace families. Where they went is never explained, but it could be potentially anywhere. They could have gone on a trip out of town for the night, they don't have to be in Haddonfield.
BaconIsMyBFF
Where did it state this was all night? It could have been a few hours. Remember that in the next one, it is still the same night and stays night through the entire movie.