Interesting, though I didn't understand most of it due to a lack of comic knowledge. I think that the element created in IM2 wasn't kept secret from anyone in particular though. It was mentioned that they couldn't make it back when Stark Sr. was alive. It's very likely that, to protect what would likely be a very important power source which would do horrible damage in the wrong hands (which he learned from Captain America), he hid the 'blueprints' of it. Of course hiding it in anything quite so simple as a blueprint design would make it fairly easy to steal. And making any real mention of it besides very cryptic clues would also give away it's location to any not-so-good people looking to make use of it. So being the rich person he was, he put the design in the buildings of his expo, which nobody would expect, and then left it for his son to discover when he grew old enough (and technology advanced enough) to understand and produce it.
That's my take on it anyways. It doesn't explain what it is though.