Make the sauce: Heat the oil in a large saucepan over medium-low heat, then add the salt pork. Sauté until fat has rendered, about 5 minutes. Remove and discard salt pork. Add onion and sauté until translucent, about 3 minutes. Add garlic and sauté just until softened. Add tomatoes with their juice and bring to a boil. Reduce heat to low and simmer until sauce is slightly thickened, about 45 minutes. Add the basil, oregano and salt and pepper to taste. Cook for 1 minute more.
Make the meatballs: In a mixing bowl, combine the beef, veal and pork. Add the eggs, cheese, parsley and minced garlic, then salt and pepper as desired. Add the bread crumbs and mix well. Slowly add up to 2 cups water, 1/2 cup at a time, until the mixture is moist; all the water may not be needed. Shape into 1 1/2 -inch meatballs.
Heat the oil in a large sauté pan over medium heat. Add the smashed garlic and sauté until lightly browned, 1 to 2 minutes, then discard the garlic. Working in batches and taking care not to crowd the pan, add meatballs and fry until undersides are brown and slightly crisp, 5 to 6 minutes. Turn and brown the other sides, about 5 minutes more. Transfer cooked meatballs to paper towels to drain, then add to the marinara sauce. Mix gently and serve.