Toss-up between option 5 and 6 for me.
I think the mandate will be struck down but I don't know if that alone would really sink his approvals as it has never been popular.
It might if he goes out and defends the mandate. If he proposes a progressive alternative (public option, Medicare buy-in, etc), I could see flat approvals.
If either of his appointees throws out any part of the bill, that would obviously be a huge Romney victory.
The only thing I could see his appointees throwing out is the mandate though the unpopular part would be deciding what provisions are linked and go out with it.
Maybe they could troll a bit and strike down the state-level mandate in Massachusetts too?