Wash the clams well and set them in a bowl. Transfer to a pot with some olive oil. Cover them and cook for about 5 minutes, until the clams open up. When the clams are open, take them out and place back into a bowl. Grab a strainer and strain out the juice in the pot into another bowl and then back into the pot, just to make sure there are no clams in broth.
Set the pot with the oil and clam juice to medium heat. Chop onion, 2 tablespoons parsley and red pepper. Let that cook down for a few minutes. Next, add the vinegar, oyster sauce, and bay leaf. Then, stir in the wine and reduce the heat to low. Let simmer for about 5 minutes. Add tomatoes and return to simmer. Cook until stew starts to thicken, about 20 minutes.
Add in the clams, fish pieces, shrimp, and the other cup of tomatoes. Stir gently and cook, until the shrimp have turned pink, 5 minutes. Remove the pot from the heat and add some more chopped parsley. Remove the bay leaf and ladle soup out into bowls to eat. Serve with a toasted buttered baguette.