so far my air doesn't give me any problem,used it a lot outdoor and in the robotic lab where it's exposed to a lot of aluminium dust and other metal.get 256gb,or not later u would regret if u have bootcamp.
they would deliver to your add,don't worry,it will reach your house safety

depends on u,i'm also using a 286ppi smartphone,well.beautiful i can say,u won't sees single pixel at normal viewing range,if u are viewing at 15cm(length of ruler) from the screen,then u will see a bit of the icon edge,but who would look at the screen so closely for long term
for me,i'm studying engineering,i need the hardware power rather than fancy display,thus i went with an i7,256,8gb ram
depends on what u do with it in the end,if u don't need processing power with <4k budget,i would get the retina macbook pro