Finally, success. Some time today Calendar.app on my iMac started working properly again. My wife's shared calendar events are showing up, the program no longer hangs with the error message "can't connect to P02.caldav.icloud.com...", events created on Calendar.app upload to iCloud.com and then out to my iOS devices as well. I wish I knew what had been done to make this work, but I'm happy that I finally have a working calendar back together. I have just sent an email to the senior Apple tech who has been my contact through this asking him if he could provide me with any additional information on what fixed the problem, and if I learn anything more, I'll post it here.
I just spent a bunch of time with Apple and have solved my similar problem. A week ago, iCal and my iPhone calendar stopped syncing. My assortment of iCal calendars were gone from iCloud, so that was the problem (not phone to iCloud). After much de-selecting and re-selecting, I realized that all my important calendars were @me.com type. I tested the iCloud calendars, and they functioned perfectly. Apple explained a simple way to migrate the @me.com calendars to iCloud:
Create a new iCloud calendar File > New Calendar > iCloud
Name the calender
Right click the old @me.com calendar and choose Export. Desktop is a good destination.
Drag the exported calendar from your desktop to the new iCloud calendar
iCal should show duplicates of all events in the @me.com calendar.
De-select the @me.com calendar. The duplicates will disappear.
Repeat with all the @me.com calendars and abandon this antiquated list.
Rejoice in your shiny new list of iCloud calendars that shows up everywhere it is supposed to.
There must be a lot of people out there who still have @me.com calendars, so I hope this info reaches them before they all spend time and money with Apple trying to sort it out.