Where was the other missile supposed to go?
Otis put in the wrong coordinates, so the missile ended up heading for Hackensack NJ.
What was its original heading?
From what we see, one missile seemed to be enough for Luthor's plan to work.
Not only that, Otis' missile kept superman busy enough that he didn't have time to stop the one that hit California. So it it worked out for Luther. Well, at least until Lois died and Superman reversed time.