Delete iCloud mail

I thought I would be able to use my iCloud email as my Apple ID.

Your Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.

Read carefully  -> How to delete your Apple ID account

How to delete your Apple ID account – Apple Support (UK)

See also -> How to deactivate your Apple ID account

How to deactivate your Apple ID account – Apple Support (UK)

Scroll to ->  How to temporarily deactivate your Apple ID

Sign in to your Apple ID account page on a Mac, PC, iPhone, or iPad. Then scroll down to Data and Privacy, and select "Manage your Data and Privacy." On the following page, select "Get started" under "Deactivate your account." If you don’t see this option, it means that this feature is not available in your country or region. 

👉 When you request to deactivate your account, you receive a unique alphanumeric access code. Make sure that you keep this access code in a safe place—you must have it to reactivate your account. 

If you forgot the access code, try to contact Apple Support -> Get Support (apple.com)

FYI: you can't merge multiple Apple ID accounts.