looks like they're using his daughter for the emotional manipulation in this case
as for Harley, it depends on which version is being used. Originally she had no powers, , later she became immune to toxins (a gift injection from poison Ivy when they started hanging out a lot). I believe the current storyline is that the chemical bath that bleached her skin also gave her enhanced strength and toughness (not superhuman levels, but more major bodybuilder levels than what you'd expect from looking at her)
as for Harley, it depends on which version is being used. Originally she had no powers, , later she became immune to toxins (a gift injection from poison Ivy when they started hanging out a lot). I believe the current storyline is that the chemical bath that bleached her skin also gave her enhanced strength and toughness (not superhuman levels, but more major bodybuilder levels than what you'd expect from looking at her)