Re: your cat. Try Rescue Remedy before you go, to see how the your cat reacts (especially as she was feral). The pre-trip prep, car ride and airport alone will probably frighten/excite it (as it does us humans). The airline asked about it's weight, to determine if the cat will fit comfortably under the seat in front of you. And yes, there is a limit about how many pets in the cabin are allowed and where they can be seated (to avoid any "misshaps"). Since you are bringing a cat on board, you might want to limit your carry-on to a minimum as the cat alone will be a handful!

(As a tidbit of information, I worked for airlines both in the cabin and on the ground)

Oh, you can also call the BVET- I did and I can't praise them enough- the person I spoke to was wonderful.