I'm running OwnCloud 9.0.x and use a Mac
1) I originally set up OwnCloud on my VPS (shared server just didn't cut it) with DreamObjects.
2) Yes, it worked on my Mac, but it was painfully slow.
3) I switched to local storage on my VPS and it's much faster now.
What I see from your description is the Web and Android client aren't doing a file sync, but more like browsing and grabbing a file when needed. The Mac is trying to do a full sync. For whatever that's worth Maybe someone has more insight. Have you tried the OwnCloud forums?