I don't know how it is packed but I bet it is not just thrown in a box. I bet it is sealed in plastic, then put in the box.
As for salt, I looked at a little snack, Camembert & Bacon Chicken Baguette. 250 grams. (8oz) Sodium 612mg, that is about a third of what you should have in a day. Why not just eat a bag of potato chips?
As for preservatives, there are at least a half dozen preservatives and a larger number of other chemical thickeners, emulsifiers, flavour enhancers and artificial flavours. Some are harmless, some troubling, like Sodium Nitrite. I will applaud OZ giving them numbers so they are easy to look up. This is the list
Chicken (78%), Seasoning (Crumb, Feta Cheese (Cheese [Pasteurised Milk, Salt, Starter Culture, Enzyme (Non Animal Rennet), Calcium Chloride (509)]), Camembert Cheese (Water, Camembert Cheese (39%) (Contains Milk) (Milk, Salt, Starter Culture, Non-Animal Enzyme), Cheese (6%) (Contains Milk) (Milk, Salt, Starter Culture, Non-Animal Enzyme), Thickener (1442), Mineral Salts (452, 339), Citrus Fiber, Citric Acid And Stabilizer (466)), Bacon (Pork (81%), Water, Salt, Sugar, Emulsifiers (451, 450, 452), Dextrose (Maize, Tapioca), Antioxidant (316), Acidity Regulator (330), Sodium Nitrite (250), Smoke Flavour, Rosemary Extract. Smoked), Onion, Spinach, Celery Salt (Salt, Celery, Anti-Caking Agent (551)), Thickener (412), Natural Flavouring), Bacon (Pork (89%), Water, Salt, Sugar, Mineral Salts (450, 451), Antioxidant (316), Preservative (250), Natural Wood Smoke), Seasoning (Dehydrated Garlic, Mixed Herbs (Parsley, Oregano, Marjoram, Thyme, Sage), Dehydrated Carrot, Sugar, Rice Or Maize Flour, Dehydrated Onion, Dehydrated Peppers, Ground Coriander, Black Pepper, Anti-Caking Agent (170), Vegetable Oil (Canola), Flavour Enhancer (635), Ground Mustard, Antioxidant (330)), Ghee
For cooking, my toaster oven would do just fine but a "happy meal" like this might be as good in the microwave if I was going to choke one down.