If you've been eating just junk, that is a big improvement. Well done. But you can improve it still further, from a general health perspective.
First off, get some fish in there. Oil fish is better than non oily fish. Healthwise this is absolutely the best way to get protein. If you're not sure the difference between oily and non-oily fish, here is a list:
Food Standards Agency - What’s an oily fish?
I am not completely sure about the malt loaf. Processed food is a bad idea in general, as the processing process invariably adds salt, sugar, fat and chemical additives.
I'd vary from potatoes and bread as your sole source of protein. Get a rice cooker and learn to use it. If you can manage brown rice all the better- a lot of the nutrients and fibre are in the brown husk that is removed to make white rice.
Don't cut butter out of your diet completely. It's good for in moderate amounts (as most things are). Some people can get vitamin D deficient if they cut it.
Try steaming vegetables, and make sure you eat them 'al dente'- when they are still pretty crisp. That way they still have plenty of nutrients in them that are otherwise cooked out.
Here's one that not everyone will agree with: don't eat meat every day. When we were evolving into our present form we didn't have meat every day in our diet and the stomach can't handle it. Most westerners, and Americans especially, have a lot of undigested meat in the bottom of their stomachs as a result. It impairs the efficiency of your digestion and is just a bit toxic.
Not sure about the cheerios. I am not wild about breakfast cereals in general because (a) they are processed, and (b) you have to have them with milk, and most milk is saturated with growth hormones (female ones) and antibiotics. A mix of fruit and organic yougurt along with something with plenty of fibre is a good breakfast. Cottage cheese on wholegrain toast is quite good if you're a bit hungrier. A few eggs a week are fine, too.
It looks to me like you're not eating too much. That isn't great because you need plenty of calories for that exercise. Also, you can get kind of depressed if you're not eating, and when you're depressed you give up. So it is better to set an achievable target that you can live with. Don't be afraid to eat a bit more. Quite a bit more. With exercise and the effects of eating right, you will get into great shape anyway.
Oh, and learn to love salads. Great way to bulk out a meal and get your vegetable and fruit content up. Don't just stick to boring lettuce and tomato. Consider any and all of white onions, avocado, any kind of nut, asparagus, artichoke, spring onions, apple, orange, olives, anchovies, and pretty much anything else that takes your fancy. Try different kinds of lettuce and also rocket, which is more bitter than lettuce and makes a nice change. Learn to make dressings as well. Although they are a little fattening in principle, in practice you can dress a massive amount of salad with a tiny bit of dressing if you mix it in first, and the effect on the taste is unbelievable- it changes it from rabbit food to something you will be wanting second helpings of. One good dressing is a vinagarette, whih you make by mixing mustard, oil and vinegar. Use nice oil (olive oil) and nice vinegar, like balsamic vinegar or red wine vinegar. Add salt, pepper, random herbs, garlic, again, whatever seems like it might be interesting.
Back from my long digression on salad...
Also, add variety. If you get bored you'll break your diet. To that end, you should invest in some healthy eating cookbooks.
(I'm assuming you don't know too much about cooking. Sorry if this is not the case and I have offended/patronized you. Not my intention at all.)