If I try for 10, 000 steps a day &eat 1200 calories, will I lose a lb. A day? Or do I need to do MORE WORKING OUT ON TOP OF THE 10, 000 steps?

Here is the key. You are ambitious and that is a good thing. Why not simply focus on eating sensibly every day, enough to stay a little bit hungry but adequately nourished, and join a group of fun-runners or do some other fitness stuff you enjoy? It is the only way you wil get lasting benefits.