shanyee - sorry to hear what has happened.
First of all - (let's get this out of the way) - you KNEW this had a very good chance of happening. Everyone has been warned and others (myself included) have spoken about it on various forums and have mentioned the possibility that your accounts could get audited. Buying tickets for other passengers (different surnames to those on the account) is risky. You know from reading the rules that miles can't be traded, and the presumption is that no one simply gives away a valuable ticket for no money in return. In your case, you clearly breached the rules by selling your ticket for someone else.
Now - what to do?
From what i understand it is almost impossible to actually speak to someone in the fraud department at most airlines. They don't really want to talk to passengers. But my first avenue would be to call and try and speak to someone. If that doesn't work, then you will have ONE chance to write a very carefully scripted letter explaining your actions, and asking for reinstatement.
That letter will probably need to go to one of their heads of customer service or something. But it will need to be a good letter - apologising for your error, and explaining it will never happen again, and asking for leniency.
The letter should also explain that the other accounts in the household had nothing to do with your actions and should be excused from the closure.
If that doesn't work, then I'm afraid you may need to seek legal advice - but that will have to be in the USA. And the hard part will be finding a lawyer willing to take on your case. And it will cost you.
There is an argument that the total closure of all your accounts, without you having the opportunity to fully explain your actions may be a breach of contract and an unfair penalty - especially to those other accounts who were not involved. (Basically - you would need to argue that one breach (if it was in fact only one breach) should not lead to such a harsh outcome).
If you want to keep your costs to a minimum (no lawyers) you need to take a complete apologetic approach to this. Hopefully you will get lucky.