Hi Bill,
I am sorry for any inconvenience this case has caused and I understand how frustrating this is for you.
To confirm that the Office 365 online services work well, I suggest you access Outlook web App (OWA) and check whether the calendar displays properly. If yes, it proves that the Office 365 is not broken.
And based on your description, I notice that you have two calendars now, Entourage calendar and Office 365 calendar. Do you mean that you have added the two accounts (Entourage/Office 365) in your Outlook client on your Mac? If possible, you can add your Office 365 account in an Outlook 2010 or 2013 for windows desktop client and check if it works well, this step will help us double confirm the Office 365 runs properly.
Thanks,
Bourne Zhang