does it make sense to get JR Pass with this itinerary?

Hi all,

I'll be in Japan from April 30th to May 8th.

My travel plan now looks something like this:

April 30th. Arrival at Narita airport. Express transfer to Tokyo, from there on transfer to Kyoto on Hikari.
May 3rd. Hikari transfer from Kyoto to Osaka.
May 5th. Hikari transfer from Osaka to Tokyo.
May 8th - Tokyo to Narita transfer.

The plan was to get 7 days JR Pass to cover all the travel from April 30th to May 5th.
But there are some questions I'm concerned about:
1. I won't be able to exchange my JR Pass until April 30th, which falls right in the middle of Golden Week, where advance planning is absolutely necessary. Does it make sense to buy JR Pass in this situation?
Or should I rather buy separate ticket somehow in advance online?
2. Is there any cost benefit from JR Pass with this itinerary? From Hyperdia seems like there isn't, but I figure there is additional cost on seat reservation when you get separate ticket?
3. Is there an exchange point from voucher to JR Pass at Narita Airport?

Thanks in advance!