I haven't listened to the commentaries yet, but does Singer explain how Supes was able to life NK into orbit when it was filled with kryptonite?
The only symbolism I can think of for that is the father doing it for his son.
It's kinda like when you read about some guy lifting a car off his kid or something like that. In both instances, the father with the car and Supes with NK, no he should not have been able to do it, but he did.
I'll give you an example: When I was in the police academy, we watched an in-car video of a cop pushing a car off of some railroad tracks just as the train cam barreling down on the car. In the car was an unconscious woman and a baby. What is so amazing about this video is the fact that in his hurry to get the car moved, HE FAILED TO TAKE THE CAR OUT OF PARK. That's right, he pushed the car with all four tires SLIDING across the pavement, not rolling. They had some physist guy say how much force it would hae taken in joules or watts or some crap like that to move the car in that condition, and he said it was impossible for a single man to generate that much force. When he watched the video, he was stunned. He still didn't see how it was possible, but admitted readily that he had just witnessed it happening.
Now, I know we are dealing with alien physiology, comic book science, etc, but I think that is what the writers were going for. When need be, ordinary men can rise to extraordinary heights, and the same can be said for Supes.