Glad you're asking your questions!
I find eating out on P1 to be destructive. It's SO hard to find all the hidden sources of sugar when eating out.
Honestly, I'd avoid it as much as possible, or just have a diet soda and then eat when you get home (or eat before). Or bring your own dressing and order a house salad without carrots or croutons.
I just find it easier to eat at home. I did 2 straight weeks of Phase 1 without any cheats (I did have some 3 bean salad on the Friday before I finished, not knowing that it had sugar in it...just had 2 bites...and it happened during the only time I ate out in P1) and I lost 28 lbs+ at the end. Just my $0.02.
You really want to have 2 straight weeks of Phase 1. If you eat sugar in the middle, you'll need to do P1 again for 2 weeks. That's a lot of time if you do it for a week before T-day. So, maybe just try to eat as healthy as you can (Phase 1.5?) until Thanksgiving and start P1 the day after?
You really can't experiment with eating off plan until you've done P2 for a while and know what you can and can't eat and still lose.