Place the mussels and clams in a large pot with a lid. Add 2 tablespoons olive oil, white wine and the water. Stir to combine. Cover the pot with the lid and place over medium-high heat, stirring occasionally, until the shells open, about 5 to 8 minutes. Remove the pot from the heat and carefully remove the mussels and clams from their shells. Pass the liquid through a fine strainer and reserve.
Pour 1/2 cup of olive oil in a 3 or 4-quart saucepan over medium heat. When the oil is hot, but not smoking, add the garlic and cook until pale gold, about 5 minutes. Add the calamari, season with salt and pepper, and cook over low heat for 5 minutes. Add the tomatoes, and simmer for 20 minutes more. Add lots of parsley, mussels, clams, chili flakes and reserved broth. Simmer, covered, for 1 to 2 minutes, then remove from the heat.
Preheat the oven to 450 degrees F.
In a large pot, bring 6 quarts water to a rolling boil and add 2 tablespoons salt. Add the spaghetti and parboil 6 minutes, stirring often. Drain and remove to a strainer in a bowl of ice water to stop the cooking process. Drain the pasta and add to a bowl. Drizzle with 1 tablespoon olive oil and toss. Spoon half of the seafood sauce over the pasta and toss again to mix well.
Using a large square piece of foil turn up all 4 sides of the foil square, forming a 3 to 4-inch wall barricade, so that the sauce won't run out. Spoon all of the pasta and sauce onto the foil square. Pull the sides of the foil in over the mound of pasta and sauce, and seal at the top to form a large package. This can also be done using 4 smaller-sized squares of foil, to create 4 smaller packages.
Place the package (or packages) on a baking sheet and bake in the oven for 10 to 12 minutes.
Carefully transfer the cooked package (or packages) to 1 large serving dish (or 4 smaller ones). Slice the top of the package open with a knife and serve hot. Garnish with parsley and chili pepper flakes.