How do I change my PRIMARY email account for iCloud?

I started with iTools, then dotmac, then MobileMe, now iCloud. Unfortunately, in the change from .mac to .me, something happened. I should be using @me.com for ALL my iCloud activities. And in System Preferences on my Yosemite Mac, it shows xxxx@me.com as my email. HOWEVER, when I go to my Contacts app and dig into preferences, it says the PRIMARY account is @mac.com. This has led to a major unexpected result: I cannot, via merge or deletion, get my iCloud contacts to sync with my iPhone contacts. NO CONTACTS on my iPhone propagate to iCloud. Other iCloud services appear to operate fine, but Contacts refuses, no matter what I have tried (and I have tried all of Apple's suggestions).

So I'm trying to reset my PRIMARY account email, which doesn't appear to be possible. In iCloud Preferences, under Account Details, Contact, I can add or delete accounts, but the delete button (a minus sign approximately 1 pixel high, so it's hard to tell when it "dims" -- thanks designers!) won't operate for the primary account.

Any ideas?