The plant should have been dismantled, flooded, and buried within 24 hours of the emergency generators going down. They knew how bad it was/is, this all could have been prevented.
It is simply not possible to dismantle a nuclear reactor that close after shutdown -- the power produced by radioactive decay heat right after shutdown is in the order of 10MW, and the core is incredibly hot for weeks. If they had done everything as well as they possibly could, they would not be any closer to dismantling the plants than they are today. The best course would have been to maintain cooling so that nothing would have been damaged -- they tried this and failed. The failures in their actions are not asking for more help earlier, not in the basic course of action they took. The idea that the reactors should have been buried with 24 hours of the emergency generators going down betrays basic lack of knowledge of the facts of the situation. Should you have tried to bury a core that has been active less than a day before without considerable active cooling, it would have simply melted it's way to the water table.
The total amount of plutonium that has been released into the environment so far is minuscule. It is significant because it serves as an unmistakable indicator that the cladding for the rods has melted, meaning that should any containment fail now, the results would be catastrophic. But we knew that -- TEPCO said that the cladding was melting on 14th of March. Still, unless something unexpected and catastrophic happens now, the nuclear side of this disaster will still kill more people in Germany than Japan.
False choice.
During those 3 months, ~250 more will die to SO2 and NOx because of increased coal power production.
Coal pollutes the atmosphere and kills miners (among other things). Natural gas has an unpleasant tendency to explode during handling, and is considerably more expensive than coal. And so on.
Nuclear may have the lowest number of deaths/power, but technically the Space Shuttle was the safest way to fly from 1977 to 1986.
I'm not necessarily that pro-nuclear, I just cannot fathom why all the outrage in power production seems to be directed towards nuclear while coal, that kills ~2700 people worldwide every day is still being used.
Note that this is not about building new plants -- this is only about what happens in the next 3 months to cover the loss in capacity caused by bringing 7 plants down.
Additionally, if you're suggesting burying it in reference to the solution at Chernoby, that also doesn't work so well. At Chernobyl the plant was effectively destroyed, so there was no harm in simply filling it with concrete and placing the sarcophagus over it. At Fukushima the plant is still largely intact. Unless you can submerge the plant in concrete in one fell swoop (not possible), the damage done by the piecemeal burying of the plant would undoubtedly create even more damage and result in more radiation leakage than we currently see.
But true, small production runs and spares is a real issue (actually, by the time they are really used, they are already obsolete -- but this is why you have upgrade plans :).