Feathers take protein to grow. I use scrambled or boiled eggs, boiled chicken, walnuts, other quality nuts. During molts this year I offered as much as they wanted , after Milt their desire for protein dropped way down. In my Ornithology thread I linked done science and research studies on molts, and the higher protein need during that time for growing feathers.
Macaw are designed to eat nuts, abd I thi k they require them more than other species. You could look I to what nuts are native to South America, and try to add a few of those. I think walnuts , pistachio, pine nuts are good, ( im not into almond )
Hot red chilli peppers are loved by many a parrot and have good amounts of vitamin A.
Taking your bird outside, shade is fine as still gets enough to help with vitamin D levels. And he needs to be protected from direct sun with his skin exposed. It is so good for mental health to be outside.
