JR East Tohoku Pass

Hi, am visiting Akita and Aomori coming December.
My flight will arrive Narita airport 8.30pm in the evening.
1. I have the JR EAST Tohoku Pass and wondering could I get my JR Pass to be validated at the airport? Is there any JR customers service counters at that hours to provide some help?
2. Could I use the JR Pass to travel to Tokyo on NEX? Or do I need to purchase the NEX ticket separately?
3. I would like to travel to Akita the next morning on Shinkansen using my JR Pass, how could I make the seat reservation before my arrival or could I do it at the airport if they have a customer service?
Thanks.

I have the JR EAST Tohoku Pass and wondering could I get my JR Pass to be validated at the airport? Is there any JR customers service counters at that hours to provide some help?

You can get your pass until 21:45 at the JR ticket counter.

2. Could I use the JR Pass to travel to Tokyo on NEX? Or do I need to purchase the NEX ticket separately?

Yes, you could use the pass, but it would mean using one of the pass' days for a 3000 yen train trip. Depending on the rest of your itinerary it could or could not be worth it.

3. I would like to travel to Akita the next morning on Shinkansen using my JR Pass, how could I make the seat reservation before my arrival or could I do it at the airport if they have a customer service?

You can also do that at the JR ticket counter.