Percy, you know that your son's blaming statements are utterly ridiculous.
But it hurts to hear them all the same, doesn't it?
I've been following your thread, your son sounds intelligent, as do you.
You've got a long three months ahead of you, and you will have to decide whether you will use the leverage of his reaching 18 to enforce your rules, and it will be a difficult decision, because 18 years old doesn't feel "adultlike" to parents.
Have you ever heard anyone look back on their growing up years and marvel at the strength their parents exhibited in the face of rebellion?
That is what you want your son to be saying in ten years.
I don't have any advice, except to reiterate what the others have said, to keep enforcing your standards and to keep up a brave front. Your son needs this kind of consistency in his life, even if he doesn't seem to agree with it, and your consistency is what he will remember.
