Hi Kyle, Your domain rhydmor.com is currently locked to the tenant RhydmorCorporation.onmicrosoft.com that you created earlier, so it cannot be reused until it is removed there. To release it, you must sign in as Global Admin of that tenant and delete the domain from Setup > Domains in the Microsoft 365 Admin Center. Since you cannot sign in due to MFA, only Microsoft Support can reset MFA or verify ownership to free the domain. Once the domain is removed, you can attach it to the correct Business Premium subscription.
This is not something you can fix locally, I would suggest you to raise a ticket to Microsoft.