JR Tokyo Wide Pass validity

I plan to go to Japan at the end of this 2015 year including 4 days in Tokyo. Is this new pass (Tokyo Wide Pass) valid for NEX train from Tokyo to Narita Airport ? and also how about the starting of the three consecutive days ? Will it start counting at the time of purchase or start from the first time using ? Thank you.

1)
Yes.

But around year end is very busy seat booking hardly usual.
NEX haven't un-reserved cars.
Try online reservation from one month before.
http://www.jreast.co.jp/e/ticket/reservation.html
However you can take any NEX as no seat(standing near door) if already full.

2)
JR Tokyo Wide based JR Kanto Area Pass with validity date info
so decide/select start day when purchasing and no sold out no worry.
http://a0.cdn.japantravel.com/photo/sbj-photo89851/1024/photo89851.jpg

Hi LDB.
Thanks for your usefull information.