The executor or administrator of the estate should have Letters issued by the Court. This gives him/her the legal right to sell the property. It...

Respectfully decline to speak with the police. If you get arrested, say nothing until you have a lawyer. There is a chance this will all go away...

If it is vehicle damage only, a lawyer would not be that helpful. If there is personal injury involved, you should consider hiring a lawyer.

Get an attorney or go to the law library and research how to prepare a declaration.

That is not valid service. With that said, unless you want a judgment against you in the states, yes you should have it set aside. You may also...

Yes, you both have the right to sue on behalf of your father for financial elder abuse.

I can tell you at this point, it will likely take longer to start over than to simply get the property in escrow and file to confirm the sale.

Pay what you owe maybe. If you have no valid defense you will lose I court.

You are correct a self represented party cannot issue a subpoena.

Yes. The only retainer you should have paid was a cost retainer. If he took more than that, it is illegal.