Q: How do I change my iCloud email address

You cannot change an iCloud address once created.  You can get another AppleID (will itself require a separate email address to create) and then create a new iCloud account with that.  But there is no way to transfer your mail from the old account to the new account.

No, sorry,  One AppleID can have one, and only one, iCloud account.

Since you cannot change the iCLoud email address once created, your only way to change it is to create a new iCloud account, and that requires a new AppleID to do so.