Linda, I think you did amazing. It is so awful to have to watch others eat delicious fatty things! My boyfriend does that all the time, and it's torture. Of course he is stick thin.
Don't worry about the pound- I'm really against weighing myself between official WW weigh-ins, but just to prove my point I did an experiment yesterday. I was 176 in the afternoon, which is 2.2 down from my last weigh in on Wednesday. After a large dinner, I was 178.4. In the morning I was 176.4. After having a small coffee I was 179.2, and after "getting rid of the coffee", so to speak, I was 177.2. Literally one minute later I was 2 lbs lighter.
So, my point is, it's totally normal to fluctuate....and I wouldn't be surprised if your fish and mashed potatoes were high in salt, so that could have something to do with it, too.
In my experience, one or 2 onion rings won't kill you. Yes, I know that all those "bites and tastes" can add up, but provided that you're not doing that every day (which I know you're not!), you will be fine. That's what the flex points are for, and besides, what is life without an indulgence now and then? It's those little things that keep you from feeling deprived and allow you to stay on plan without bingeing.