Wow, I really loved this analysis. It's so coherent and clear on reflection, I really have trouble believing any other interpretation is as accurate.

I absolutely love Majora's Mask. It is one of my favorite games of all time, I'll have to watch this when I'm able to

Something I've always wondered is why Majora / the mask / the skull kid decided to rob Link, and I think this analysis sheds some light on it. If Majora is a physical representation of unresolved childhood trauma, it makes sense to me that they steal his horse and ocarina: these are precious things, but they are also reminders of his traumatic past. I have felt the contradictory urge to destroy or dispose of things that are precious mementos because they also carry associations with painful memories.

Trauma also emotionally stunts you and can make you appear childish to others even when you feel like an adult, which is why Majora curses him into the form of the Deku child.

I also love how Link learns to come to terms with his trauma. First, he must do what he must to survive, which means getting his ocarina back and getting himself into a position where he isn't faced with the threat of imminent death, which he does by remembering the song of time. Once he himself is in a safe state, he goes about methodically helping everyone he can find who needs help, and asks for nothing in return. For these deeds he receives masks, memories of good deeds that he has done. Finally, in order to fully self-actualize, he gives these masks freely to the children on the moon.

One of the children on the moon asks Link if he will become a mask salesman. I think a mask salesman, in the context of the game, is someone who has amassed great wisdom but hoards it, only sharing it selectively with those who can offer something of value in return. Instead, Link gives his masks away. Not only that, he gives away every non-transformation mask he has, getting nothing in return (as far as he knows). If he can do this, he learns from the Majora child how to become the Fierce Deity.

I think it's fascinating and thematically beautiful that Link can defeat Majora without becoming the Fierce Deity. You don't have to be a Buddha to overcome trauma. But if you can learn to share the wisdom you have gained by your suffering, and ask nothing in return, then the fight becomes much, much easier.

P.S.
Something that occurs to me as I'm writing is that this game also shows Link's journey experiencing empathy. When he encounters the body of the Deku child, he doesn't really understand what he's looking at. By the time he meets the ghost of Darmani, he has acquired the tools he needed to heal himself, and is able to use them to heal Darmani as well. With Mikau, he rescues him from the water, hears his dying wish and honors it, eases his passing, gives him a proper burial, and mourns him. That's a considerable evolution.