1) Well, not quite. because a superatom's valence is akin to that of atoms different to itself, it takes on different chemical properties, though not necessarity different material properties.
Quite aside for its radioctivity, Plutonium is chemically one of the most toxic substances known to man. A superatom of another element might duplicate that, without being radioactive, but it wouldn't be useful for a reactor.
What makes a nuclear fuel desirable is the energy latent in it. Unfortunately, that energy is released when its nucleii break apart into smaller ones, which radiate away from the point of separation.
2) Now, a superatom that behaves electrically like gold sounds more feasible. Whether it would be less expensive is something to be determined. The more we research it, the less it should cost to produce.
3) Hmm. What we're looking for here is density, and superatoms of anything have multiple nucleii per atom, so it would be more dense. This definately seems like something worthwhile. Sheilding perhaps even more dense than lead, with different chemical properties from lead, so it isn't environmentally hazardous.
Here's a question, though: how stable are superatoms? If some normal atoms break apart when bombarded with radiation, might not many superatoms?
Oh, that's what you meant by substitutes for Uranium. Hmm. Wouldn't it take as much energy to produce as you get from it? It might still make a better battery, though, in terms of power to mass ratios...
4) New light weight materials seem unlikely, though, given the reasons mentioned above.
