Have you tried side step. I put in DC to Tallahassee and got back the lowest fare of $432, but I don't know what dates you had in mind. I tried the 11th through the 13th. Delta was the cheapest for those dates and route.
I'm waiting a little longer to see what happens before scheduling a trip. We are thinking about driving, but haven't firmed up anything yet.
Yes, I think my problem is no seven day advance. I'm also thinking of driving, but would have to leave Saturday afternoon. That's still an option.