Interesting philosophical question :)

[EkoFox]

Wild, if the odds that any one person would cure cancer were the same, then those four men have four times the chance to cure cancer than that one man.

So: Yes pull the lever, either inaction kills four or action kills one, preserve 3 more lives.
No don't punish him, by doing a small infraction of theft, he did the greater moral good of saving a life.
Yes push the guy, same as first question.