Hey there,
I would suggest making a detail table. So have three rows for social, political and economic and three columns, one for really basic information (like dates or a summary of an event etc.) one for quotes and one for statistics. This will make it easier for you to summarise all your content and to structure your response. Disclaimer: I personally found it useful, however, if you're a visual person then mind maps would be a great way to show how all the events link together.
As for the essay question, make sure that you're explicitly stating your thesis in your first sentence, regardless whether it's an essay or an extended response. Since it's an extended response, structure it like a mini essay. You could structure your response like this:
1. Thesis (first sentence)
2. Point 1 (e.g. "This is reflected through the way the Romanov Dynasty responded to social issues, greatly contributing to the fall of the Romanov Dynasty).
3. Elaborate (this is where your detail comes in. Going back to social issues, maybe you could assess Tsar Nicholas II's attitudes towards multi-ethnic backgrounds and the russification, or the distinct social classes).
I'm not sure how many marks the extended response is worth, but assuming it's around 8-10 marks, you should probably be aiming for around 3-4 sentences elaborating your point. Then you move on and assess how the political and economic issues contributed to the fall of the Romanov dynasty. When it comes to the actual details, you don't need to constantly refer to statistics. You could also refer to events such as the poor outcomes of the Russo-Japanese War, which led to the 1905 revolution and the Tsar's response to the revolution made their autocratic system fragile.
Hope this helps!