Thanks for trying the system.
The demo indeed freezes when you talk to John outside in winter. This is an error in the demo though, this should not effect your project at all. I should fix this some time. :p
The time is not shared in between save files. It is based on the players play-time, so that should not be possible.
You could show the time trough a hud, but there is a big downside to that: The time only changes when you run the common event. So if you want the time to update every second, the common event has to run every second. This can cause lag.
Freezing time when the menu is open or during cuts cenes is also a hard knocker, because the time is based on the players play-time.
Waking up at 6am should be perfectly possible. Just calculate how many hours are left between the time they go to bed and 6am, and let that be the amount of hours they sleep.
I'm happy you like the system. :)
Oh, and happy new year!