First of all congratulations on your recent marriage!
It seems that the problem arose when you did not give the lender your new address and perhaps fell behind in the payments during the extension, or exceeded the 5 month extension.
Your parents were not notified because co-signors never are notified of ongoing problems. They are only notified after the repossession is complete, the auction is complete and you fail to pay the deficiency amount. Then the demand is made on the co-signor for payment.
You asked: how to do i fix my and dad credit (cosigner) as this was an honest mistake AND am i responsible for the difference when sold if sold less then msrp?
All you can do is be prepared to immediately pay the deficiency amount following the auction of the vehicle, if there is one. The deficiency will include your remaining lease balance and any past due amounts, the costs of repossession and for any damages to the vehicle or additional mileage charges if the car exceeded its allowed mileage during the lease term, and for the costs of preparing the car for auction---think cleaning and detailing.
You may reply back to me using the Reply link and I will be happy to continue to assist you until I am able to address your concerns, to your satisfaction.
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I wish you and yours the best in 2016,