The foods on the website are given out by (i think) EAS who now owns the program/contest and are NOT authorized by Bill Phillips (BFL author). EAS just want you to buy their stuff and get into the program, so they authorized more stuff. Sticking to the list in the book is your best bet. Admittedly I use some FF dressing once or twice a week, but because of the sugars it contians (as do 99% of fat free items) you should avoid it as much as possible. They just wanted to make the plan easier and more mass appealing.
As for cottage cheese, go by the Protien grams for your serving. I eat 20-25g of protien at a time and that works out to about 1 cup of cottage cheese. Yogurt is a carb and you should do the "fist in water" dispacement test to find your serving. I use between 200ml and 250ml (2/3 to 1 cup) Yogurt is not a very filling carb tho, and many kinds are high in added sugars for the flavoring. Make sure you read your labels
I eat "by the book" as much as possible. If you have any specific questions about foods go ahead and post, im sure there are lots of ppl who can give you feedback
Hope this helps!
Tidey