1. Preheat broiler.
2. Cut bell pepper in half lengthwise; discard seeds and membranes. Place bell pepper halves, skin sides up, and whole poblanos on a foil-lined baking sheet. Broil 10 minutes or until blackened, turning poblanos to blacken all sides. Place peppers in a zip-top plastic bag; seal. Let stand 10 minutes. Peel. Finely chop bell peppers. Cut tops crosswise from poblanos; remove seeds.
3. Heat a large skillet over medium-high heat. Add oil to pan; swirl to coat. Sprinkle shrimp with 1/4 teaspoon salt. Add shrimp to pan; cook 3 minutes or until done. Remove from pan.
4. Add garlic to pan; sauté 30 seconds, stirring constantly. Sprinkle with flour and ground red pepper; cook 1 minute. Slowly add half-and-half, stirring with a whisk. Stir in 1/2 cup milk; cook 1 minute, stirring constantly. Remove from heat; let stand 2 minutes. Add cheese and 1/4 teaspoon salt, stirring until smooth. Place 1/3 cup cheese mixture in a large bowl; reserve remaining cheese mixture. Add bell pepper, shrimp mixture, cilantro, and juice to 1/3 cup cheese mixture in bowl; toss to coat. Stir 1/4 cup fat-free milk into reserved cheese mixture. Spoon 3 tablespoons cheese sauce onto each of 4 plates. Spoon 6 tablespoons shrimp mixture into each poblano. Place 2 stuffed poblanos and two tops on each plate.