Other mistake: When Superman and Lois are flying through the clouds, there are a number of shots in which we see Superman from Lois' point of view. If you look closely, you can see that Christopher Reeve is not being suspended in these shots, but is, in fact, kneeling to look as though he is flying. You can tell by the profile of the red trunks.
Other mistake: During the subway scene, when Dorothy, Tin Man and Scarecrow are trapped behind the red fence, there is no lock on the door in the fence. The door bounced once before falling shut, so it's probably not stuck. So how are Dorothy, Tin Man and Scarecrow unable to push it open?