Four weeks travelling Japan!

Hello there,

Starting to use the JR Pass once you leave Tokyo is a great idea. I also love the visit to Nagasaki. Its a very nice city to visit and there's a lot history to be found and it's also home to many beautiful sights. You are also making great use of your JR Pass by going all the way down to Kyushu. Did you have any question in particular? As I think the itinerary looks great!

As for the JR Pass, I would go for the 21 day JR Pass the only problem is that it would expire before you return to Tokyo.
The best option would either to reschedule a little and be back in Tokyo by when it expires. Another option is to go a little more crazy and add a 7 day JR Pass. This opens up a couple more extra options, for instance a visit to Nikko from Tokyo or tour a little more around Kyushu, for instance you could visit Aso-san, or go all the way down to Kagoshima.

Enjoy Japan!
Daniel