Hi there!
As a 14 day pass is ¥45,100, you'll need to spend at least this on JR tickets for a 14 day pass to be worthwhile. Lets look at the base price of your travel excluding your possible return to Osaka from Tokyo:
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Tokyo > Hakodate: ¥19,140 (365mins, 878km)
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Hakodate > Niseko: ¥5,210 (166mins, 179km)
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Niseko > Sapporo(jr): ¥2,100 (166mins, 106km)
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Sapporo(jr) > Tokyo: ¥22,770 (551mins, 1196km)
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Tokyo > Odawara: ¥3,840 (35mins, 83km)
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Odawara > Tokyo: ¥1,450 (36mins, 83km)
JR ticket cost: ¥54,510 for 6 legs
Note that for Hakone the JR Pass will get you as far as Odawara. From here you'll need to use the non-JR Odakyu lines upto and around Hakone itself. I recommend the Hakone Free Pass for this which can be purchased on arrival into Odawara.
If you didn't do any further travel than the above (and could cram all the travel into 7 days), the a 7 day pass would make a lot of sense. If you did the Tokyo <> Osaka/Kyoto trip, then a 14 day pass would certainly be worthwhile. You'd also be able to use the pass on all the JR lines around Tokyo.
Hope this helps!
