http://blog.lefigaro.fr/hightech/middle-earth-map.jpg

Hello. Apologies if this isn't in the right section. I need a refresher on place name hierarchy and scale. It's a bit hard to describe so let's look at the Middle Earth map.

Question 1. Compared to Earth, how big would Middle earth be? Is it one continent like Europe? (Arda being the world)
Question 2. Would Rohan/Gondor/any of the medium size fonts be the size of a country?
Question 3. Does Nation, Kingdom and Realm etc pretty much mean the same thing?
Question 4. Is it alright to use 'Country' for medival/fantasy maps? If not, does Land = Country?

I have a lot of obscure questions so hopefully you can understand what I'm trying to ask.

Thanks.