I only do sociology at GCSE, but going off what I know, for the first question I'm assuming you'd have to say how functionalist sociologists believe that the nuclear family is positive for society for these reasons: reproduction, primary socialisation, economic support. I'd also say about how New Right Sociologists would say that children from nuclear families do better at school, are less likely to turn to crime, and get better jobs.
I don't know about the second question, but maybe mention cohabitation?
Perhaps mention the media for question 3.
And I can't think of anything for the last question.
Hope this helped in some ways!