Prepare the broth by combining all ingredients for dashi in a large pot. Bring to a boil over high heat. Reduce heat and simmer for 20 minutes. Remove from heat and strain the broth, discarding the mushrooms, anchovies, and other seasonings. Set aside.
Heat 1 tablespoon vegetable oil in large wok or pot over medium-high heat. Add sliced pork loin and cook until no longer pink, about 5 minutes.
Add all of the vegetables including carrots, onion, zucchini, green onion, cabbage, leek, and mushrooms. Cook until softened, stirring frequently, about 6-7 minutes. Add garlic, ginger, and Thai chile and saute for 30 seconds.
Stir together sesame oil and hot pepper flakes in a small bowl. Add to cooked vegetables along with 5 cups of the broth and stir to combine. Cover and bring to a boil. Reduce heat and simmer for 10 minutes.
Add shrimp, clams, and squid to the pot. Cover and let the seafood simmer gently in the broth, about 4-5 minutes or until the clam shells have opened and the squid is pink. Season with fish sauce, soy sauce, and black pepper. Adjust seasoning, adding more fish sauce and soy sauce if needed.
Cook fresh noodles as directed on the package. Drain and portion noodles into 4 bowls and ladle soup on top with the seafood. Serve immediately.