Obon travelling and transport in Tokyo

I'll be arriving in Japan from Korea by ferry on 13th August. I plan to stay with a friend in Kitakyushu for 1 night before going to Toyko by shinkasen on the 14th. I have a few questions:

1) Will I be able to get a seat on the train to Tokyo on the 14th, and what are the best times to leave? I plan to leave in the afternoon.
2) Will there be other obon festivities in cities like Kyoto/Osaka/Tokyo, and how long will they be? I assume it's the one where there are street stalls and fireworks and people wearing yukatas? That way I don't have to go to Kitakyushu (my friend told me that's only a festival for the 13th itself).

3) Lastly, I was wonderin if I buy the JR Pass, if I can use this pass taking the subway around Tokyo?

Thank you very much!

Will I be able to get a seat on the train to Tokyo on the 14th, and what are the best times to leave?

Being in the middle of the Obon holidays, I don't think that travel activities will be extremely high, and I suspect that you could be able to make seat reservations on the day you arrive in Japan. Alternatively you might want to ask you friend to buy the tickets for you before your arrival. Not using a Japan Rail Pass would make that process easier. Note anyway, that a single one way trip from Hakata to Tokyo is cheaper than a rail pass.

Lastly, I was wonderin if I buy the JR Pass, if I can use this pass taking the subway around Tokyo?

No, you can only use JR trains. But these include urban JR trains like the JR Yamanote Line, which is convenient for getting around central Tokyo. But it does not include the subways.

Hi Uji, thanks for your reply. I've decided to reach Kitakyushu on 14th August and leave the morning of the 15th to Osaka. I was planning to buy the JR Pass but am worried I may not be able to get seats on the 15th if I don't reserve my ticket since it's Obon, and if I''m not wrong, I can't reserve tickets till I reach Japan. Can anyone recommend if I should get the JR Pass or just pay the normal fare?
My planned routes are Kitakyushu-Osaka, Osaka-Kyoto and Kyoto-Toyko. THanks again!

see above