1. In typical nuclear fuel, about 3.5% of the uranium is fissile (U-235), the rest is not. Only this 3.5% takes part in the energy production. As a side effect, also some of the rest decays, but not much.

2. Fuel cell production is very little in the price of the creation of the nuclear energy. Thus, it is not a really important question.

3. The technology is ready to use nearly 100% of the uranium content (google for: breeder reactors) since about the 60ties. Main reason of that it is not widely used, that it is not very needed because (1), but is being labeled "experimental" and causes additional unrest because (2).