Many questions!

Hi there,

I assume it will be exchanged at the current rate. I think your itinerary sounds fine for a JR Pass as well.

I would suggest making reservations as soon as possible if you prioritise wanting to sit next to your friends. If you have the option to book them online with the JR Pass I'd suggest doing that.

You don't have to pay extra for the Shinkansen with the JR Pass - if you want to, you have the option to upgrade some certain services on some lines that are faster, e.g. the Nozomi on the Tokaido Shinkansen. However, this is definitely not a necessity as the Shinkansen is already very fast and the Nozomi is mainly there for commuters (hence why it is not included in the pass).

Hope this helps!

Alexis