Hokkaido, Tokyo, Osaka

While you would get your money's worth buying a 14 day JR Pass, it would mean spending an excruciating 9-10 hours on the trains getting to Hokkaido from Osaka, completely murdering a whole day for you.

A smarter choice would be to fly from Osaka to Hokkaido, and come back using a 7 day JR Pass.
There are cheap fares on low cost carriers like Jet Star for as low as ¥4890 one way. Another possibility is on ANA's Experience Japan Fare.

Then you can return on a 7 day JR Pass, stopping in Tokyo along the way.

For Tokyo, the Tokyo Tower is OK but you can get the same view for free from the Shinjuku Metro Gov't Bldg. Roppongi Hills is another choice. The best view though is from the newer Sky Tree (but pricier as well).
For Osaka, you have things mixed up. Namba is in Osaka, the other places are all in Kyoto.