Combine the first 6 ingredients. Shape mixture into 16 (1-inch) meatballs; place on a broiler pan. Bake at 450° for 12 minutes or until done. Combine yogurt and the next 4 ingredients (yogurt through sugar) in a bowl. Arrange 4 meatballs, 1/2 cup greens, and 2 tomato slices in each pita half. Drizzle each pita half with 1/4 cup yogurt dressing.