Considering that Johnny is in the air, it would be difficult for him to literally run into Satan; he does, however, seem to be heading in a trajectory that takes him over what appears to be just a varitable cornucopia of corpses. And, steadily pushing towards the inner city, gore-soaked and moving with mechanical efficiency, is Satan.

It turns out that the chest-punching thing works fairly well on whatever creatures actually have hearts. The ones that don't have essentially the same thing occur, just at head-height instead.

Lucifer doesn't appear to notice one measly human on an ass-engine dragon, because he has more important things to do, like kill things. And, really, that's probably for the best.