first, as tactfully as you can, communicate the idea that without scholarship money, you won't be able to attend the school. this kind of argument is made more powerful if you have a competing offer with scholarship money.
second, very clearly explain all of the extenuating circumstances that make the FAFSA EFC unrealistic for you. i'm not sure if you have or are expecting any unusual expenses in the coming year, but if you are, detail those.
just keep in mind that almost all schools expect most of their students to take on some amount of debt to finance law school, so don't be surprised if the school comes back to you and says no.