I think it's a fairly ordnance heavy IN fleet. Not a bad thing. I'd swap out the firestorms for swords since I think you will get better performance from 3 swords than 3 firestorms.
As far as how many models make an AC squadron, as long as it's recognizable as what it is then as many models as you want. (you could even write "bomber" on it and that would be good) The print out chits have 5 for fighters, 3 for bombers, and 4 for assault boats.