Where is the meat? Beef, chicken? No, a bacon roll doesn't count.
Where is the seafood? Fish, shellfish ?
Where are the cereals? The pasta, rice? Industrial baked goods such as brown toast ,and the various crackers do not count. Is porridge home made or sachet?
3 vegetables? Where are the leafy greens? Spinach, broccoli, carrots pumpkin, cauliflower....
This is not about variety , it is about diet quality, a diet that promotes a heathy brain development and a healthy body.
It is prevalently sweet, especially with the dry fruit, raisin, dates, prunes, biscuits, breadstick, jam....
Diet is about giving nutrients. As you realised, since you made this post, this a poor diet. Remove all the crisps, biscuit, breadstick, crackers to start with. Those might come back later as an occasional treat, but as long as they are there, you will never be able to make changes.
Try a homemade or butcher bought schnitzel, meatballs in sauce, prepare and offer a variety of vegetables, cooked and raw, not just a sliced cucumber.
Put out of sight, the fruit bowl. Cut down on food two hours before meals. Even fruit or milk.
Make soups that are sweet tasting at first, such as pumpkin-carrot-onion, make a broth, and cook baby egg pasta in it, and serve it with some real parmesan and a tiny 1 cm cube of butter.
A sole cooked in butter, with a sprinkle of chopped parsley and a tiny bit of salt is irresistible.
Of course, there will be resistance, but involve him in the cooking process.