You might sue for repayment. Does the contract you have specify that you are to have possession of the vehicle if the co-buyer defaults on this...

If you have the agreement in writing, then 6 years is the statute of limitation. See an attorney; a number of exceptions exist

No.....................................................................

A will is valid if among other things it is witnessed by two witnesses. A notary is not required, but a self-proving affidavit does simplify...

Not sure what you mean and seems light on facts. Consult with a real estate attorney............................

It might. See an attorney.............................

The notary is right. Forgetting your middle name is unlikely to invalidate a power of attorney.

If you have other debts and assets to protect, you might consider bankruptcy.

Have you talked with a debt attorney about bankruptcy as a way of clearing your debts? The privacy issue seems like small potatoes.

If someone knowingly sold you a car that was not theirs to sell, this is fraud. See an attorney.