I doubt that is the only evidence, but the answer is yes, he can be charged by word of mouth. Another name for word of mouth is witnesses. If the...

I was wonder if i qualified for the 10-15 days a month good time credit under the first step act

Those programs do not yet exist. But when they do, 841 is eligible.

You can be indicted any time within the statute of limitations, which for most federal crimes is 5 years.

Plea deal?

It depends on the circunstances. Typucally, once you are sentenced, the sentence controls, not the plea deal.

Can you be charged with drug conspiracy if the other person is in prison ?

Drug conspiracies can be committed over the phone. One conspirator can be in prison.

Can a state prisoner be released from the county jail if he is still there on his release date?

If he has completed his sentence, he will be released from the jail.

Using the 5th amendment as a witness legally.

A witness can assert the fifth amendment if the questions they are asked would tend to incriminate them. If you believe you have a fifth amendment...

Ask for a presidential pardon for federal crime?

You can ask for a pardon once your sentence is done, but the typical waiting period is 10 years to show you have been rehabilitated. Your chance of...

You absolutely should hire a lawyer. What the police tell you is not binding and you are not protected. You are right to be concerned.

Yes, they can lie to you. And they cannot guarantee you will not be charged. You need an attorney who can negotiate an agreement with a prosecutor.