1) There was a clock hanging in the hallway, so it wasn't an issue. But I'm sure it differs from one test center to another. I'd take a watch with you to the test and just keep it in your pocket - no one will know it's there. Then once you're outside, you can look at it. But, this 10 mins flies by quickly.
2) My test center had a lock with a key.
3) Yeah, I'd definitely bring a snack...the whole she-bang can take up at 5 hours, including registration time, so you need to keep your blood sugar up. Don't bring anything that needs preparation/heating, though. I know my test center had a microwave, but no one used it, and I don't know if other test centers have it. I just brought a Subway 6 inch, and my 10 min break was just enough to run to the bathroom and then eat.