Combine chicken, the juice of 3 limes, chipotle peppers, adobo sauce, 1 tablespoon olive oil, garlic, salt, and pepper in a bowl. Marinate for 20 minutes to 1 hour.
Preheat a grill pan to medium-high heat. Coat tomato halves and corn with remaining olive oil and grill until blackened in spots, about 8 minutes. Cool until easily handled, about 5 minutes. Dice tomatoes and cut kernels off the corn cobs. Transfer to a bowl; mix in avocado and 1/4 cup cilantro.
Grill chicken until no longer pink in the center, about 7 minutes.
Meanwhile, place brown rice in a bowl. Mix in remaining lime juice and cilantro. Season with salt and pepper.
Remove chicken from the grill pan. Grill tortillas until crispy on the edges, about 2 minutes per side. Place each tortilla on a serving plate. Layer brown rice, chicken, lettuce, tomato salad, and tomatillo salsa evenly over each tortilla.