I would get copies of the trust documents and the actual deed to the house. I would guess that your name is somewhere in the trust documents.
Then I would take these down to the ATF offices the next time you're in FL. Talk to them and establish that you do indeed meet the requirements of being a resident while in state. Ask if they could verify this for an FFL over the phone so that you may carry out your purchase. Something in writing would be even better.
FTF deals are another option- the issues are finding what you want and not being able to show someone state ID if they ask.