As to exactly "Why" Edward goes into this display instead of remaining in a sitting position, your guess is as good as mine. I would suppose the hunting instinct has its own adrenline-type rush and Edward is compelled to act on it, burning off some of the energy in a non-lethal way.
I think you are spot-on here, Corona. He needed a release. As he finds out later, as long as he channels that excess, finds a different way to release that need, than he is more than capable of loving Bella safely.
But, I think Ginnie's point was more that being able to read Edward's "thoughts", what was actually in his head in those minutes and hours, would just be beautiful. It's one thing to understand his thought process, to see why he did and said what he did. It's entirely another to be able to see it through his eyes. THAT'S what we're all waiting for.