Welcome to the forum,lots of good members here who'd love to help. You should read through some of the older threads in the amazon section amd gain some insight into your new companion.
About your OWA, they mate for life and depend on their flock to look after them. You've taken away the most important things in his life and turned his world on end. Similar to you losing your spouse. His cage is the "rock" in his world right now. Keep it near the center of activity in your home. Talk to him and try to include him in daily activities,engage him,show him your fun and interesting. Instill some desire to be with you. Amazons mate for life and he just lost his so it might take a while for him to come around. Practice stepping up if he shows a interest,but don't take him away from his cage(safe spot), step up and quickly back down to the cage. Don't have him step up to go somewhere else or to cuddle with you,you might get bit. Biting is generally his way of saying no. Learn to read his eyes,stance ,tail feathers etc. He's giving you clues to what he's thinking but you haven't learn to read them yet. When he starts to come around to you,don't smother him with love,kisses,pets,etc. show him some affection but only for a short period, leave him wanting more of your attention ,not him biting to say "that's enough".
Food, daily maintenance pellets are best,they should make up a large part of his diet, the rest should be fresh fruit/veggies,sprouts,some nuts and seeds. Seeds and Nuts are high in fat and amazons store fat in their liver,active flighted or breeding birds burn that fat off, clipped caged birds don't. The excess fat store in the liver causes problems and most pet zons die from fatty liver disease. It's not just from sunflower seeds and peanuts but also fatty human food,french fries ,buttered toast,and junk foods that people eat.You can try feeding him small portions of your dinner if he shows an interest (many do) but make sure it's not covered with fat ,salt,sugars etc. Needs to be healthy. I'd try feeding small pieces of things like banana,apple,grapes etc from your hand while he's in/on his cage. I could write a book here but will try not to , all of this stuff in already in the forum in some of the older threads, read around and learn alot. Ask questions in the amazon section, hope to see you around. capt and Jake the YN