Changing icloud nickname
How could I change my icloud address: xxx@icloud.com ?
Under certain conditions, you can login to iCloud.com using xxx@me.com or xxx@mac.com. But, if you want to make a significant change, then you will need to change your Apple ID. I suggest going here to change your Apple ID: https://appleid.apple.com/#!&page=signin You would need to change it so you use a 3rd-party user name such as xxx@yahoo.com. But, before changing it, read:
Changing your Apple ID: https://support.apple.com/en-us/HT202667 and
What to do afterwards: https://support.apple.com/en-us/HT204071