Preheat the oven to 350 degrees. Prepare a 9x13 baking dish with nonstick cooking spray. Melt the butter in a skillet over medium heat. Add the onion, celery, bell pepper, and green onions. Saute until soft, about 6 minutes. Add the garlic and cook for 1 more minute.
To the vegetables, add ½ cup of ketchup and mustard, stirring until blended. Remove from heat and allow to cool for 10 minutes. In a large bowl, combine the beef, sausage, bread crumbs, eggs, evaporated milk, 1 tablespoon hot sauce, 1 tablespoon Worcestershire sauce, seasonings, and vegetable mixture.
Mix well by hand until evenly combined. Transfer the mixture to the prepared 9x13 baking dish. Shape into a loaf. Bake uncovered for 1 hour or until the internal temperature reaches 165 degrees.
Meanwhile, mix the glaze ingredients until blended. Brush on top of the meatloaf with the ketchup mixture and bake for 5 additional minutes. Remove from the oven and allow to rest for 10 minutes before slicing and serving.