choice of a pass

Hello,
we are going away to Japan in September for around 2 weeks. We will be visiting Tokyo (3 night), Hakone (1 night), Kyoto and Fushimi Inari (2 nights), Hiroshima (1 night), Osaka (1-2 nights), back to Tokyo (1 night). Passes are quite expensive therefore I would like to make sure which one we should buy. After reading one of the letters ('Yen - 2 Week JR Pass') and the answer to it I am not sure which pass would be the best for us. Could we actually get away with buying a 7 day pass instead of 14 days one? I can still rearrange the order of places which we are planning to see if that would help..?. Finally, what are the luggage restrictions when boarding on the train? Are they always the same?
Many thanks.
Marta