Hi there,
For a 7 day rail pass to be worthwhile you need to spend over ¥28,300 on JR tickets. For a 14 day to be worthwhile you need to spend over ¥45,100 on JR tickets. Lets take a look at your projected costs based on your itinerary:
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Tokyo > Odawara: ¥3840, (35mins, 83km)
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Odawara > Takayama: ¥12710, (240mins, 448km)
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Takayama > Kanazawa: ¥4380, (186mins, 148km)
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Kanazawa > Hiroshima: ¥15550, (265mins, 605km)
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Hiroshima > Miyajimaguchi: ¥400, (26mins, 21km)
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Miyajimaguchi > Kyoto: ¥11310, (165mins, 402km)
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Kyoto > Tokyo: ¥13420, (161mins, 513km)
¥61610 for 7 legs (14 day pass)
14 day rail pass (¥45,100) saving: ¥16510
¥48190 for 6 legs (7 day pass to Kyoto)
7 day rail pass (¥28,300) saving: ¥19890
As you can see, both options will give you good savings over standard tickets. Based on your itinerary alone, a 7 day pass coupled with a single ticket from Kyoto to Tokyo will give you a total cost of ¥41,720 and would be the cheapest option. However if it is likely that you'll do a further ¥3380 of JR travel, or you would prefer the flexibility of a further 7 days free JR travel, then at a further cost of ¥3380 a 14 day pass is clearly worthwhile.
Please note that with a 14 day pass you'll be able to also include your travel from Narita airport in the JR Pass if that is where you arrive/depart, which would give a further ¥3000 savings. You can also make good use of the JR Pass within Tokyo. Here's a map of JR lines in Tokyo for reference.
You can look up precise train timetables and costs at the Hyperdia travel planning website and learn how to use Hyperdia through our video blog.
Hope this helps!