Yes this could be malpractice. Malpractice means that a doctor violated the standard of care. A bad outcome is not enough. Another doctor would...

No. You can sue the other party if they are in breach of your agreement.

You can sue the buyer of the vehicle.

You may have an accounting malpractice case. Consult with malpractice attorneys.

Get the garnishment papers and look at the court case. You were probably sued and a default judgment entered against you.

If he eventually paid you what was proper he will not likely forfeit his fee. But, you can report the unethical actions to the State Bar.

Losing a case is not a reason for a bar report or a legal malpractice lawsuit. Malpractice means that an attorney violated the standard of care. A...

If you only have disability, you probably are not required to pay anything.

Unless there was an agreement for a late due date or payments made within the statute of limitations, it is too late to sue.

More clarification is needed. But, one does not pay for mistakes caused by the other parties accounting mistakes.