No way would Patsy have covered up for John if he had killed her precious daughter. In that case, I think Patsy would have killed John.
I would agree on #1.
Re # 2 : imo John did not revise anything, but merley did what Pats ytold him to do. He let her run this staging show from start to finish. I don't believe he thought they would get away with it. He probably was in some numb, fatalistic state of mind.
He must have been to think that RN was going to fool anybody- the odds that anyone would believe that note are so minimal- yet here we are