Ryan North of the webcomic Dinosaur Comics asked his friend Ben Tippett to write a formal paper explaining the coherency of Superman's amazing powers. It's a very math and physics-heavy article, so I won't try to understand, let alone summarize the whole thing. Here, however, is the conclusion:
Link via io9
Image: flickr user chanchan222, used under Creative Commons license.
We conjecture that all of Superman's powers come from His ability to alter the inertial mass of objects in His immediate vicinity or with which He is in personal contact; although the mechanism is unknown.
Link via io9
Image: flickr user chanchan222, used under Creative Commons license.
http://www.dailytexanonline.com/life-arts/mad-league-upset-with-hero-for-defying-laws-of-physics-1.968046
Force of will.
bulletproof = dense sub protonic structure which also makes him quite heavy.
Haven't read the whole thing, just the intro/conclusion and it would appear that Superman would be a Telekinetic due to the following: "...alter the inertial mass of objects in His immediate vicinity..." Not buying it, no sir, try again.