Hi again,
1.) Shibaurafuto Station is served by the Yurikamome line which unfortunately is owned by an other company than JR.
The closest JR station is Tamachi, which is 1.3 KM walk from Shibaurafuto.
2.) Sorry not that I am aware. I did some searches for you but could not find any bus.
3.) The JR-Pass can be used a range of bus routes and local buses, here you can find bus routes that are covered.
4.) The express way is only a car road, without a pedestrian walk. I actually tried getting on there myself as well from Odaiba, I walked all the way until the water between Odaiba and the rest of Tokyo to find out I could not :(
However I great walk from Odaiba to Tokyo is via the Rainbow Bridge if you walk it after nightfall you can see a beautiful view of Tokyo and Tokyo Tower.
Sorry that it is so hard to get to Odaiba by the JR-Pass, I wish they would make a Shinkansen station there so you could ride there in style.
Best wishes,
Daniel