A:AnswerProbably about 8 feet, I'm about 10 and its fine. There should be no danger closer, just that you'll see more of any blur, pixelation and such. That's where 4K can help.
A:AnswerThe dimensions are 27.4 inches high, 12.2 inches deep and 43.3 inches with the stand. Without the stand the height is 24.8 inches and the depth is 2.4 inches.
A:AnswerNot without buying extra stuff like a Chromecast and using external programs that would cast a mirror of the PC screen to it. I would just get a 50ft HDMI cord and hook it directly to your video card. I do that and it makes a great monitor.