Hakone to Shinjuku

hi all,

planning my trip now for March-April and would need some clarification / advice:

from Kyoto, planning to take Shikansen using JR to Odawara. I'm planning to stay in Hakone for 3 nights before going to Tokyo.

should / can i;

1. take the romancecar from Hakone back to Tokyo? or does the romancecar only go a single direction from Shinjuku to Hakone only? if it's only a single direction, how to i go to Tokyo?

2. is 3 nights too much for Hakone / Fuji area? i derive to 3 nights simply because i'm guessing when i reach Hakone, it'd be already noon to late afternoon so not exploring too much on that day. exploring is during the next 2 days.

thanks and looking for some feedback and advice :)