7 Days Japan Rail Pass Itinerary

Hi Daniel,

I plan to go to Japan with the following itinerary:
20 Oct - Kansai International Airport
21 Oct - Osaka
22 Oct - Osaka
23 Oct - Osaka to Nara (Round Trip)
24 Oct - Osaka to Tokyo
25 Oct - Tokyo - Karuizawa (Round Trip)
26 Oct - Tokyo
27 Oct - Tokyo to Nikko
28 Oct - Nikko to Tokyo
29 Oct - Narita International Airport
I will use the pass to cover my last seven (7) days in Japan (i.e. 23-29 Oct).

23 Oct - Osaka to Nara (Round Trip)
Even though I will activate my pass on this day, I will probably not use any JR train at all because the access from my hotel to Nara is easier by Kintetsu line.

24 Oct - Osaka to Tokyo
I will use shinkansen from Shin-Osaka to Tokyo by Hikari.
When will be the fastest day I can reserve my seat for Hikari? Is it 23 Oct (i.e. when I activate my pass)?

25 Oct - Tokyo - Karuizawa (Round Trip)
I will use Hokuriku Shinkansen Hakutaka to travel to and from Karuizawa.
Reservation is mandatory on Hokuriku Shinkansen.

26 Oct - Tokyo
I plan to go to railway museum at Omiya and will utilize shinkansen to go there since my son is a fan of shinkansen.
I plan to ride Tohoku Shinkansen Hayabusa and Akita Shinkansen Komachi.
Reservation is mandatory for Tohoku Shinkansen but not mandatory for Akita Shinkansen.

27 Oct - Tokyo to Nikko
28 Oct - Nikko to Tokyo
I plan to ride Tohoku Shinkansen Tsubasa to go to Utsunomiya and then continue with JR Nikko Line.
How could I make a reservation for JR Nikko Line? Can I use the green machine or at any JR ticket office as well?

29 Oct - Narita International Airport
I plan to use NEX to go to Narita International Airport.

Based on the rides that I plan, I need to make a lot of reservations.
Should I make all reservations in advance at one go since my itinerary is quite fixed?

Thanks in advance, Daniel!