In a medium mixing bowl combine ground chuck, breadcrumbs, milk, beaten egg, 1 teaspoon Italian seasoning, 1/2 teaspoon dried parsley, 1/4 teaspoon red chili flakes, 1/2 teaspoon onion powder, 1/4 teaspoon granulated garlic, 1 teaspoon salt, and 1/2 teaspoon black pepper; mix gently until evenly combined.
Cover the meatball mixture and refrigerate for at least 30 minutes to firm up.
Heat 2 tablespoons olive oil in a large pot or Dutch oven over medium heat. Add the 4 thick-sliced garlic cloves and cook until soft and fragrant, about 1–2 minutes, then remove and discard the garlic pieces from the pot.
Add the 28 oz tomato puree and 28 oz diced tomatoes to the pot, then stir in 1 1/2 teaspoons Italian seasoning, 1/2 teaspoon dried basil, 1/4 teaspoon red chili flakes, 2 teaspoons salt, and 1/2 teaspoon black pepper.
Reduce heat to low, cover, and simmer the sauce for 25 to 30 minutes. Taste and add up to 1 tablespoon sugar if the sauce is too acidic.
While the sauce simmers, preheat the oven to 425°F (220°C). Line a rimmed baking sheet with foil and spray with non-stick spray.
Form the chilled meat mixture into 1½-inch meatballs and place them on the prepared baking sheet about 1 inch apart.
Bake the meatballs for 10 to 15 minutes, until browned and cooked through.
Cook the spaghetti in a separate pot according to package directions until al dente, then drain.
To serve, place spaghetti on plates, spoon marinara sauce over the pasta, top with meatballs, and sprinkle with grated Parmesan and chopped fresh parsley.