Factual error: About 11 minutes into the film, Luthor's yacht is seen in heavy seas in the Arctic. The helo on the helo deck has its rotor blades extended. This would cause immediate damage to them so is never done, even on carriers - the helicopter wouldn't be able to fly properly. (00:11:20)
Factual error: Jimmy tells Clark that Luthor was freed from jail because Superman didn't appear when the Court of Appeals called him as a witness. Court of Appeals rulings are based on the facts in evidence from the previous trial, and nothing else. No new evidence or testimony is allowed.
Factual error: The shuttle attachment to the plane is wrong - the shuttle undercarriage would not be part of the fixtures. Not only that, when we see the undercarriage raise into the shuttle there are no wheels, so the shuttle would not be able to land upon its return, also the the undercarriage poles change shape before and after release.
Answer: There are two stories: a) the suit was made by Martha Kent from the blankets which came with Superman when he was a child and these blankets got superstrenght from the sun too. b) Superman generates an aura which protects him and his suit against such forces. Both stories can be true: either the suit itself is weakend by the kryptonite or Superman's aura was weakend by it. Currently it is said that the blanket-story is the correct one. Also, they don't actually cut it off him - it appears to open along a predefined line (coupled with someone exclaiming "got it!"), presumably the method Superman uses to get into the suit himself.
Bjoern_Buller