Im sure you dont have t odestroy ALL of the targets? its been a while though so i could be wrong. Just destroy as many as you can, and then after that strafe with your guns. As for wingmen.... have some more faith in them
This is one particular game where i find the AI are actually of some use.
Just make sure you have them set to "attack primary target" which is down on d-pad (select all squadron) then right on d-pad (attack primary).
Hope this helps.