1) Button remains online 30 seconds after you closed the window.. auto-login is on by default ("Remember" checkbox)
2) I tested sound in FF under Mac and Win, will check in Ubuntu as soon as I install it...
3) yep, will do. Yellow X with confirmation on the right, near the agent name (only if feature "Ability to ignore visitors from the queue" is on)
4) no way... yet
you really need to disable it?