Your first question intrigued me. Wikipedia (if it is correct) has the following: "By the mid-20th century, it became customary to display strings of electric lights as Christmas decoration detached from the Christmas tree itself, along streets and buildings. In the United States, it became popular to outline private homes with such Christmas lights in tract housing beginning in the 1960s."

I also thought this articles was interesting (though it's mostly about tree lights), and it includes interesting source links: http://www.oldchristmaslights.com/timeline.htm