Can I be arrested if I sign a affidavit for my uncle saying the gun found in a no knock warrant is not his?

No one can answer that without more facts.

This is a scam. There is no lawyer, no diplomat. Google is your friend.

It is up to your parents who you date, but he is asking for trouble.

Car crash under influence, woke up in hospital. Police never gave me back i.d is that bad?

Is it bad that you were driving under the influence, had an accident, and the police were involved? Yes, that's bad.

Not a legal issue. Just block him...

Not much info on which to give an opinion.

You mean like voodoo? Yeah, I don't think there is anything you can do about that.

Yes they can. Stay away from her until she is 18.

What is the procedure to use someone for dsflammation, false narrative to harm reputation

You have no grounds for a lawsuit IMO.

If anything, the opposite is true. Military members are held to a higher standard.