Changing ea accounts on same console

I am receiving 1:860015:89001S:9C:-13561655840 on my sons battlefield 6 profile on the Xbox s console. I see that this is ongoing for months and many people found creating a new account and signing in with that one seems to resolve the issue. My problem is that his account was set to a child account through the Xbox. I am unable to log in via the Xbox or a different device or browser. Support will not allow me to log in anywhere but the console. I am unable to unlink the account from the game. I also am unable to complete the linking process to manage his account FROM my parent account for this same reason.

A cycle of support agents told me I should be able to log in via bf6 or the ea app. I can’t purchase the ea app because his account is a child account. I can’t purchase it for him because I am unable to complete the linking process.

Will someone please for the love of god help me. I need a way to create a new account and for him to be able to play on an xbox s. I do not care about saved game data loss, (he has none). I don’t understand how to do this. Please treat me like a veteran with PTSD and little tech experience.