Very nice update, Chantel! Sounds like Nike is making his preferences known. Some adult birds avoid the unfamiliar be it diet, toys, humans or housing.
I don't doubt Nike is on the lower end of his perfect weight scale but there is a wide variance in size among species, in other words, a lower weight could be Nike's norm, considering his background alone, he could probably stand to gain a little weight. Try not to get frustrated with the chop, keep being persistent and creative, chop, shred, dice, grate, add a drop or too of coconut oil, repeat! Quinoa or brown rice or even whole grain or vegetable pasta will sometimes make the awful vegetables more palatable. Soaking pellets in organic fruit juice diluted with water is also a good trick that often works.