Yes, if the judgment was properly renewed. Review the court file where the judgment was entered and in any other state it was domesticated.

Yes you can sue for a refund of money paid that was not owed.

The representative of your father’s estate can request a report from the attorney. The Bar association may also be able to assist.

You could have a malicious prosecution type case. But, the DA is likely immune from a lawsuit. You can look for attorneys out of the County...

You are responsible to pay the reasonable value of services which may be much less than the amount billed.

There may be a conflict. Contact the Bar Association and they may investigate.

Contact the police. The threat and doing so are both crimes.

This would be an odd way to approach the case. If you are not on the fee agreement you should explore this further.

No, you may simply serve the interrogatories. No advance permission or any filing is required.

Yes. Public disclosure of public facts is a tort in many states. There would be a question as to what harm you suffered due to the disclosure.