If your mechanic has narrowed it down to a MAF sensor then I'd go with his/her result. A code doesn't mean that's the actual problem. Codes only help you in the diagnostic process....not something to soley rely on.
Have you checked the rear brake pads?
That sound is probably because the shims are dirty or something. Apply some Brake-Quiet to the front and rear faces of the brake shims.
Lugs being torqued in the wrong sequence may cause the rotors to be warped? Are you sure? It's possible that the face that meets the hub gets warped but I just can't see how the actual braking surface to brake pad face can become warped because of an improper torque sequence. Care to explain?
If you're aiming for an all weather, over-all well rated tire....I'd go with Kumho ASX...I've had them and I love them. For a performace/sunny tire, I'd go with Bridgestone Pole Positions.
If you're going to occasionally drive it then go for the 6. If it's only going to be her and she's not going to notice anyways then I'd settle for the 4.
As from personal experience. I'm not a big fan of the newer Toyota engines. I hate how they all have the visible thin layer of oil residue when you open the oil cap. Oil seal leak issue's seem to be much higher than Honda's.