Lebanese Fattoush Salad with Grilled Chicken

Name: Lebanese Fattoush Salad with Grilled Chicken
Ingredients: Salad; 2 6-inch whole-wheat pitas,split; 3 tablespoons extra-virgin olive oil, divided; 1 ¼ teaspoons ground sumac (see Note), divided; ¼ cup lemon juice; ½ teaspoon salt; ¼ teaspoon freshly ground pepper; 1 large head romaine lettuce, coarsely chopped; 2 large tomatoes, diced; 2 small salad cucumbers, or 1 large cucumber, seeded and diced (peeled if desired); ½ cup thinly sliced red onion; ⅓ cup thinly sliced fresh mint; 1 1/2 pounds boneless, skinless chicken breasts, trimmed pounds boneless, skinless chicken breasts, trimmed; 1 ½ teaspoons extra-virgin olive oil; ¼ teaspoon salt; ⅛ teaspoon freshly ground pepper