His bond will probably be revoked on the first case due to the new crime.

If he is in jail in federal custody, he had a detention hearing and a judge ordered him detained with no bail. Federal cases take a long time. He...

What are the chances the feds going to pick up a gun charge in Tennessee?

There are many factors that go into whether the feds will pick up a case. There is no way to say in the abstract. Get a lawyer.

How does my probation find out if I leave the country?

Attorneys are not going to help you violate your probation. You will find out soon enough how you get caught.

Possible sentencing outcome for conspiracy to posses with intent to distribute oxycodone first offense?

Your lawyer would be a great person to speak to about your likely sentence,rather than attorneys who know nothing about your case.

Do they have to prove evidence?

Yes, they have to have evidence. They may have wiretaps, texts on his phone, fingerprints, and informants. If they had no evidence he wouldn't be...

As long as the product is legal, you do not need permission to send it to strangers.

The Speedy Trial Act did not begin to apply until he was taken into federal custody. The situation you describe is that the state picked him up,...

My brother is serving his 15 year sentence and was wrote up for conspiracy with mail which he had no idea about any suggestions?

It is unlikely the prison will believe he received drugs but knew nothing about it. Typically drug dealers expect to be paid

Can states use something you said against you?

Yes, they can use your own statements against you. That is called a confession.