gravity pull will have no effect once converted to being a permanent, as they have no hitpoints and cannot sustain any damage. it would be easiest to just remove it from the card as it is irrelevant, just like poison. adrenaline and momentum would remain.
consider that a single act of permanent control can be used to remove the petrified creature from play, this is why the cost is lower. it has limited use on your own creatures: protect them from cc, give more room for other creatures, have it not be absorbed by chimera. offensively it could be used to move a creature to be then PCd, this would be a two card kill combo (this + pc card)