This sounds like a very spoiled bird! He will learn to eat better, but you have to be consistent with him and stop giving in. A lot of owners claim they have tried everything and their bird just won’t eat better. But any good Avian Vet will tell you they have never failed to convert a bird to a better diet within 7-10 days. I think your best option is to find an Avian Vet who will convert the bird for you. If you have failed after 2 year, you are probably not going to change. It takes tough love, and some owners just can’t do it. As a chick, this bird should have been given a variety of foods to learn to eat starting at around 6 weeks old. Instead of hand feeding, you put these foods in the cage and leave the bird alone for about an hour. If he can see or hear you, he will just beg for formula. When this is done before each feeding, the chick starts trying foods and is weaned within a few weeks. But at 2 years old, I have no experience with a bird that has been kept on formula for this long. You are right, the nutrition is not what he needs. He is getting too much fat for one thing, and this will cause him to develop heart disease and /or fatty liver disease. He needs a full workup by an Avian Vet, and needs to eat an adult diet. This really is the best way to go.
Thank you for asking Lafeber,