Duo is very smart in doing so ^_^
We en wij. When do you use which?
It has to do with emphasis, the difference is explained here in detail. Since there is not context in Duolingo, in most cases it does not matter which one you use.
How do you know whether 'women' is meant to be formal
The formal word for women is mevrouwen.
Is steunen more like supporting financially, ideologically or both?
I think both. http://dictionary.reverso.net/dutch-english/steunen