How can I get help proving unlawful search and seizure?

Candidly, the way you get help is by hiring a lawyer. Your post contains several misstatements of the law, and you simply are not in a position to...

Block the phone number, block them on social media, throw away their letters etc.

You can't. The bank has no reason to release you from your obligation.

Your son's lawyer knows much more about the case than we do.

Only a judge can make the final determination, but I am going to guess the cop will say he consented to the search.

If the case was closed without charges, you should be able to call NCIS and get your phone back. But if the investigation is still ongoing, they...

Can a premptory challenge go forward if the written motion hasn't been submitted to the court?

I am not trying to be sarcastic, but you are trying to learn 3 years of law school and years of practice on your own. You can't.

Lawsuit?

You have no grounds for a lawsuit under these facts.

Can I sue and or press charges?

You cannot press charges. Only the DA can, upon recommendation by the police. But you can sue him for damages, assuming he has any money to collect...

You can use the Find a Lawyer tab at the top of the page.