I'm half Polish half Norwegian, and have lived in Norway for my entire life. I've lived in a place where dialect is the common language spoken and written. It's kinda similar to Nynorsk but all over it's very different. I find it easier to write Bokmål than Nynorsk although Nynorsk is more similar to my dialect, if you know what I mean! But I have to say, not every Norwegian understands the more unique dialects in Norway. I mean, everybody understands the dialect from Trondheim, Finnmark, Bergen, Stavanger and so on, but I often find myself translating from my dialect to Bokmål because of the fact that people that (most often) speak Bokmål don't understand my dialect.
You have two alternatives I believe, the church or NUK(young Norwegian Catholics). I find it easier to meet other Catholics and poles through NUK.
No, their often described as "Polske arbeidere" or "Polakker" which means "Polish workers" or "Poles"
That comment about "polske arbeidere" or "polish workers" I find quite condemnatory(prejudice), this is what poles with a low-paid job are called in Norway, and it's like calling every Norwegian rich because of the oil. My dad(from Poland) is a doctor and has lived in Norway for 25 years. I've told people that I'm from the north pole just for fun, I'm from north in Poland. It's ok as a joke, but I wouldn't use it in a serious setting.