84 on 70 in GA w/ FL license. What are my options to avoid impact on my insurance, points, girlfriend's insurance etc.?

Hire a lawyer, and get the charge reduced to a city ordinance violation or county ordinance violation.

Is it possible, I have a defense for driving on an expired tag - while trying to "ready" my vehicle for inspection?

No. This is not a defense to this charge.

Yes. File a warrant application for her arrest. You will need witnesses who heard her say this.

I am wondering what punishment I will be facing? If it is severe, what can I do?

This is not fast enough, in and of itself, to suspend your license if you are at least 18. The best thing you can do is ask the prosecutor to...

These places are not legal. Nothing will be done to anyone who has a phone number listed there as that is not enough.

What will most likely happen to me, and what can I do to help myself in this situation

You will most likely be fine since your case is in juvenile court. Juvenile court usually works with people to dismiss the charges, and remove...

What are the chances of you getting probation in the state of Georgia if you haven't been arrested in over 15 yrs

Probation is a good bet. You may have even better options available to you. In either event I seriously doubt you are going to get any jail time.

For a YouTube prank video, would it be legal to go up to random people on the street and lick their elbows?

This would be considered battery as it is an unwanted and offensive touching.

What is considered a threat over text?

This, most likely, is not a threat.

What can I do with this situation?

We need much more information to answer your question.