How much radiation is Japan really getting and how long does it stay active?

The half life of the radioactive dust is many years. The dust is being spread around the world, but it only takes one particle to instantiate a cancer tumor. This event is now considered a level 6 event on a scale from 0 to 7.

To learn how to reduce the growth of cancer tumors, read "The China Study" by T. Colin Campbell.

Unfortunately, there is a lot of misinformation about the nuclear problem in Japan going around and a lot of it is in the media. Things you are not considering, Japan is not a third world nation. They designed their reactors to survive what is considered worst case scenarios (aka think of the worst tragedy you can and then add another). Their reactors not only survived an 8.9 magnitude earthquake but additional aftershocks of 5+ (normally semi-large to large earthquakes on their own). Not only that, but the reactors then survived yet another catastrophic event, a tsunami larger than anyone ever expected. They evacuated people for safety reasons and then expanded the radius when meltdown became (continues to be) an issue. They continue to look out for their people by suggesting updates to the evacuation distances (see second link for more information).

I suggest if you want to see how nuclear reactors really work and how bad the danger is in Japan you should read the link below. Suffice to say, Japan's awesome engineers kept the plant from a total meltdown and now have the long process of decontaminating some radiative steam and sea water. Processes which are not ideal but we know how to handle.

In regards to your question about radiation released, here is an excerpt from the link below:

"As mentioned previously, steam and other gases are vented. Some of these gases are radioactive fission products, but they exist in small quantities. Therefore, when the operators started venting the system, some radioactive gases were released to the environment in a controlled manner (ie in small quantities through filters and scrubbers). While some of these gases are radioactive, they did not pose a significant risk to public safety to even the workers on site. This procedure is justified as its consequences are very low, especially when compared to the potential consequences of not venting and risking the containment structures’ integrity."

Or from an updated post today (second link):

"At 8:37PM on March 14, in order to alleviate the buildup of pressure, slightly radioactive vapor, that posed no health threat, was passed through a filtration system and emitted outside via a ventilation stack from Fukushima Daiichi Unit 2 reactor vessel."

"TEPCO workers continue to pump sea water at 1, 2 and 3 reactors. “The biggest problem is how to maintain the cooling and how to contain the fire at No. 4.” At 10:22 a.m. Japan time, the radiation level between units 2 and 3 were as high as 40 rem per hour. “We are talking about levels that can impact human health.” Edano said."

Which is why they have been monitoring the situation and evacuating people while trying to discern what was really being released. Longer lived stuff would be aerosol cesium and iodine, so whatever their half-life is.

Well, they just had an earthquake, so you should think about that. Wel, it's probably 'cause of the ocean tides, or the plated underground, or the weather.

it will be absorbed by the people living near the site, and the fish in the sea