I had a 1st Sergeant in the National Guard who was an FBI agent as his full-time job. Once we sat down and had a heart-to-heart about an upcoming drill, as I was bucking for a debate scholarship and needed to go to state finals. We reached an agreement about what was/wasn't important, I won the state championship (novice class) and thought all was good. Then I found out that what he told the CO was 180 degrees different from what was said in the conversation, and I lost rank in the incident (administrative reduction -- something they can't do on active duty).
The big thing I got out of that experience is that
FBI agents lie whenever they feel like it. Note that it's a felony to lie to an FBI officer (or any federal agent, isn't it?), but he's already started lying to you (12 po-po + 2 ATF? Do you really believe that? If they had a warrant, they wouldn't have called it off over a phone call...). What happens if he decides to lie again and say you agreed to/admitted to/confessed to something else in your conversation? Who's a judge going to believe?
Get a lawyer, and have him broker the transaction. At a minimum, have a lawyer present during all questioning/conversations, so you'll have a record of what was/wasn't said.
Understand that I'm a little more paranoid about law enforcement than most -- in that same NG unit I had cops that bragged about framing innocent people when they "copped an attitude," so I'm a little more sensitive about the possibility of abose-of-power issues than most. Not trying to be a paranoid nut -- just trying to get you to think this through, as talking to this joker
at all is foolheardy, in my opinion.
Oh yeah -- keep posting. You're 2 posts away from a thousand posts. Doesn't Rich have to buy you a cake or something?
(edited because I can't type.)