Which JR Pass to get?

Hi,

We're planning on spending a month in Japan, and this is the first version of the itinerary. (I looked closely at the suggested 21 day itinerary on japan-guide.com :). I have tried not to backtrack too much!

1 Kyoto Arrive in Kyoto
2 Kyoto
3 Kyoto
4 Kyoto > Nara > Kyoto (daytrip to Nara, train 30min)
5 Kyoto
6 Kyoto > Mount Koya (morning train for 3 hours, overnight at a temple)
7 Mount Koya > Osaka (noon 2 hours)
8 Osaka
9 Osaka (daytrip to Kobe, train 20mins, Rokko mountain)
10 Osaka (daytrip to Tottori desert?)
11 Osaka (maybe a night at Kinosaki Onsen?)
12 Osaka > Hiroshima > Miyajima (morning 2 hour train, Hiroshima Peace Park, Tadanoumi, 40 minutes)
13 Miyajima > Nagasaki (train at noon 4.5 hours)
14 Nagasaki
15 Nagasaki > Himeji > Nagoya (morning train 4.5 hours, castle, 90min)
16 Nagoya > Ise > Takayama (90mins, ise shinto shrines, 4.5hours)
17 Takayama
18 Takayama > Kanazawa (noon train 2.5 hours)
19 Kanazawa
20 Kanazawa > Tokyo (morning train, 4 hours, 1 change)
21 Tokyo
22 Tokyo > Kamakura > Tokya (daytrip to Kamakura)
23 Tokyo
24 Tokyo
25 Tokyo > Nikko > Tokyo (daytrip to Nikko)
26 Tokyo
27 Tokyo
28 Tokyo > Bangkok

1. Is there too much travelling in some parts? (especially the middle - day 12 to 16 to Nagasaki and back)
2. Would you recommend a 21-day JR pass? (and which date would it be active from?)
3. Or would a 14 day pass be more cost efficient (maybe from day 9 to day 22?)
4. Or would it be better to get a combination of regional JR passes?
5. Any observations/suggestions about the order in which towns are visited?