how much dough should I use for a pizza crust?

I agree with sdb; you should easily get 4 out of it. Since you're using a bread dough, do be sure to stretch is as thin as you can so it isn't too doughy; otherwise, you may have trouble getting the crust done before the toppings overbake.

How much flour is in your recipe? I get two pizzas out of a recipe that uses three cups flour + 1 cup water + 1/4 c. oil if that helps.

I think it would make 4 pizza's with a thin crust. I could be wrong usually just make a recipe for pizza dough that makes one pie.