tacit and others may be interested in learning how your problem was fixed.
Except I'm not sure I have anything meaningful to offer, as the Apple support person did all the work. Quite a bit of it was while I sat on hold and he tinkered, getting the iCloud to recognize my Apple ID and Password.
Having established that connection, he had me sign in and sign out. When I gasped about signing out, and losing all my calendar entries, he said not to sweat it. Sure enough, when I signed back in, the Calendar re-populated with all my entries, save a few made in the last several days.
So, bottom line.... I'm not free of iCloud but at least I have minimal involvement...and the aggravating pop-up is gone.
Curiously, several days ago (prior to the Apple support fix) my iMac began coordinating mail with my iPad. That is, if I deleted an email on one, it would be deleted on the other. They have never done that....ever.
