Combine pork belly, 1 red chile pepper, lemongrass, 3 tablespoons fish sauce, 3 cloves garlic, 1 teaspoon MSG, 1 teaspoon white sugar, and five-spice powder in a bowl. Cover with plastic wrap and refrigerate until marinated, 1 to 3 hours.
Mix 1/4 cup fish sauce, 1/4 cup sugar, 1 red chile pepper, lime juice, 5 cloves garlic, and 1 teaspoon MSG together in a bowl. Let sit until dipping sauce flavors meld, 30 minutes to 1 hour. Pour in water.
Thread the marinated pork belly onto bamboo skewers.
Preheat grill for high heat and lightly oil the grate. Cook pork skewers, turning occasionally, until crisp, 8 to 10 minutes. Serve with the dipping sauce.
