From images on the internet you can get that in reality it would be around 6 meters wide (something between 5.5 and 6.5 meters depending on which image you look at) and 11 meters long (that's stated on the wiki).

This build is 29 blocks wide (and 1 block is 1 meter wide), so 29m / 6m = 4.83
So it's built in 4.83:1 scale

I honestly don't know. I try to find a happy medium between correct size and detail. I usually build slightly larger than 1:1, but I don't measure the scale

Thank you, sir!