3 hots, 3 neutrals, 3 grounds; so confused
Your switch is fine

The switch is fine -- it just needs to be wired correctly.  Keep the neutrals nutted together, and pigtail the ground to the switch's ground terminal (I have no clue why a black wire got landed on a ground screw in the previous configuration, but it was clearly wrong).  (You can strip your existing 12AWG white pigtail bare and reuse it for pigtailing the ground, BTW.)  Then take the feed (3) and the bathroom (2) black (hot) wires and nut them together to your black pigtail, which lands on one switch hot screw.  Finally, land the remaining black wire on the other hot screw.