Here's my first question: Is there a turning back and reporting them as fraud?
Response 1: There is a "turning back." However, you cannot report the grandparents as fraud because they were not the ones that stole your information, their grandson did and that's who you would be reporting to the authorities.
No payments have yet to be authorized. What would be the ramifications of doing so in addition to tanking my credit score?
Response 2: Nothing apart from your credit score being affected if the credit reporting agencies do not resolve the disputed information in your favor.
2. Since that time the perpetrator used my accounts I did not know he had acquired... a Home Depot card number, a Lowes card number and he hacked into my checking account by linking it to a Target debit card. I AM reporting these to the authorities and have been working with the marshal service. His grandparents are aware and have told me to turn him in... which is why they are now FUDGING on paying the previously mentioned cards in #1. I want them to keep their agreement.
So here's my second question: how do I minimize the damage to my credit score by reporting these last three card numbers as stolen? Does it make a difference that it was the numbers and not the cards themselves?
Response 3: No, it does not. If the information has been stolen, you have to promptly report it so that you would not be held liable for it and your credit score would not be affected because you can dispute the information on your credit file with the credit reporting agencies.
My bank credited my account and said this fraud was not as SERIOUS as ID theft which is what happened with the first 3 cards I am paying off. They did tell me that they would not report anything to my bureaus but that other vendors that deal with fraud probably would.
Response 3: If reported then you can dispute the information so that it would not be held against you.