Maybe he just wants some freinds to jam with but nobody hangs out with someone horny without some gold and threats on the line, tales as old as time really.
It's not the heat but the pressure that does it. The heat in a star is the byproduct of the pressure, it's not what causes the gold to form. And even then I think metals as heavy as gold only form in a supernova.
I always thought that Johnny won the contest, but Johnny's pride will eventually land himself in hell anyway, pride being one of the seven deadly. Devil doesn't care that he lost and doesn't flip out for that reason.
I always thought this but with the added twist that the Devil didn't actually lose. He chose to "lose" because he didn't want Johnny humbled. He wanted Johnny and all that pride to go across earth challenging anyone to believe they could be so good as to beat the Devil, inspiring more pride.