There is no definite cure, i used 2-6-5-1 1-3-4-2 3-4-6-1. and for the " Slow firing weapon with no assistance" you find the other weapons ingame, i finished with 6 different guns and all i had to do was hold down the button and the zombies would be splattered. +
My problem is, the defense games may be fun at first but the way i see it is : i shoot a wide arc of lightning up to 3 spaces infront of me, i should be able to hit something twice my size that is less that 3 STEPS infront of me at least 1 time in 4 turns