Greek Fava with Grilled Squid Recipe

3/4 cup yellow split peas; 3 tablespoons extra – virgin olive oil , divided; 1 small red onion, finely chopped; 2 cups vegetable broth, or water, plus more as needed; 12 ounces squid, cleaned (see Ingredient Note); 3/4 teaspoon salt, divided; 1/4 …