Great thanx for that. Ok, you can try a few things and see if it helps if you want.
He's quite young still, and i would suggest moving his cage maybe to a room where you can just close the door when he wants to sleep. I found that my own bedroom worked the best.
Then the time you interact is very important. Try spending two 1 hour sessions with him and i found putting my baby to bed by 6:00 helped alot. They were in a routine at the breeder and she probably put them to bed at that time. Give it month by month and stretch by half an hour each time until you reach 7:30, it is also the ideal time when their adults to let them go to sleep.
When you are finished with him for your 1 hour session put him in a closed cage so that he can sleep or sing to himself, he is after all still a baby and you dont want to pop your head in every 10min to see if he is still on his cage.
He will have to be away from the other birds for a while, you can take him to them when you have him out, but when you interact with them and he is there he might grunt/moan. That is not for attention, he wants to rest.
Watch out when you want to pick him up, that he isnt too low from your hand. I found that my boy thinks i want to slap him, and give him your flat hand not finger. Never hit him on the beak or point a finger when scolding him. He will lunge.
When taking him out, keep him to your chest/belly area, i know he likes your shoulder but for him to feel safe and you to interact more thoroughly i would suggest you start out that way.
I'll think of more things as i see your posts. This is only hints, this is how i worked with my boy as i also were new to the big bird world. We tend to forget that they mature slower than small species. As i said, you dont have to do what i suggested, but you can try out a few and see how it works for you.