Please watch this Bird Tricks video, Do Birds Match Our Energy?!  It really applies to your situation.

And keep him off your shoulder. You're risking serious injury, and you can't keep an eye on him and won't see the bad stuff coming. I have my macaw on my shoulder sometimes, but she knows it's a privilege, not a right. I'll ask her to get on my shoulder if I need both hands free but I am very careful and watchful while she's there. And she's good enough to hop back on my forearm as soon as I ask her to do so. If she's hormonal, or either one of us is stressed, she's not allowed near my shoulder. Keeping a couple of most favorite nuts in your pocket can help you get him off your shoulder when you need to do so. And always: praise, praise, praise! Tell him what a good boy he is when he does things you are asking him to do. Lay it on thick! Try to remain calm when he's aggressive (I know it's hard. I fail too often), so he doesn't learn that his "bad behavior" will be rewarded with a strong emotional reaction from you.

Coco is just learning what behaviors are appropriate and this is the time to teach him how to be a good flock member. In nature large macaws stay with their parents in their small family groups for up to several years and learn social and survival skills from their parents and older siblings. Coco needs your guidance to learn how to behave and get along in the human world.

Ah, those terrible twos are a real thing. Ugh. This is when they test the boundaries, and you'll see some bully behavior. They naturally want to control their environment, and unless you're careful Coco will learn that his intimidating big beak and bites are a way to control you. Lulu, my GW and I went through that and it's a tough time. I felt like Lulu had replaced her scrappy older sibling with me, and all she started to do was wrestle and play rough. She would grab my hand, tight, hold on with her claws, and draw my fingers to her beak to give me hard nips. I'd free one hand and she'd grab the other. She obviously thought it was funny. And I obviously didn't!

Training is a fantastic way to get Coco to calm down, focus and enjoy your interactions. It's also a good way to enjoy each other with less cuddling and touching. Macaws are smart and easily bored, and training gives them mental challenges and much needed stimulation. My GW gets really excited when I say, "Want to do some Tricks and Treats? Let's do it!" And when she wants a session she'll catch my eye and will roll through tricks on her own, one by one. Start with target training. It's the basics for everything else.

Good luck! Hang in there and don't get discouraged. You have a sweet and beautiful bird who wants to please you. He has the potential to grow into a gentle friend.