Correct about the soup. I'm not sure how many points it is for more than one serving, but it can't be many. And yes, its Core!
Progresso has some zero point soups that are quite hearty, but again--you have to watch how many servings you have.
Strawberries are a great "0 point" snack, but again, if you are getting into massive amounts, you must calculate points. But you can have quite a few for no points.
You're doing Flex? I don't know for sure but I think the recipe in the book (if I remember correctly is) makes about 4 servings, so one serving is 0 points but if you eat more than a cup you'll have to start counting points. This soup is a Core food so if you are doing Core then you could eat your fill without worrying about points. I think you have an excellent strategy in having a cup of soup before your meal. I personally have a big appetite so eating a salad or soup before my meal does help. Good luck to you.