1) that's what is supposed to take place. Choosing "guest" logs in the user as a limited access "guest" without any effort to identify the specific user.
2) you'll need to explain how your "masking" fields are designed since such a feature is not a built in feature of FileMaker. If they use script triggers, script triggers cannot be tripped via user interaction with the browser like you can from a FileMaker client.
3) What are you using to host your database? FileMaker Pro or Server Advanced? I suspect you'll need to change system settings on your host so that it never sleeps.