Well, dxb, I couldn't find the article, but. For what it's worth, I'd always thought of quintessence as the ultimate, most perfect example of something, as in: Bach's compositions are the quintessence of Baroque music.
By the "fifth element", did they mean besides earth, water, fire, and air? I haven't any problem with the term repulsive gravity; repulsion is, after all, the opposite of attraction. So of course things would move away from one another. Your question on where the supposed energy field came from intrigues me. Here's my theory, based on your phrase 'at the moment of the big bang': that the bang created an energy field, and since energy can move faster than objects, that this field swept out ahead of whatever celestial bodies were on the move. Like a shock wave raditates out first when a bomb has exploded.