Answers to your questions:
1. No
2. No
3. Using the miisclient, I see that it runs a "delta sync" every 3 hours. That's what I was referring to. The only visible error message from that tool is "stopped-extension-dll-exception". That is what led me to look at the event viewer to find out what was going on. The OU users are the only ones I'm viewing under Users and Groups and they are showing as "in cloud" (I deleted all of the others after I deactivated AD sync). While the full sync doesn't appear to be working, if a user changes their password, the change is synced.
We're running the latest DirSync tool (assuming a new one has not been released since Friday when I installed it). Where would I find "Start-OnlineCoExistenceSync"?
Thanks!
Susan