Radiation Protection in Space

Radiation will go through two feet of lead, so how do we protect astronauts on the other side of the Van Allan Belt? Mother Earth is doing that right now by being a magnet. This same magnetic protection can be duplicated in the infrastructure to house astronauts.

It has to be fact. Living in zero gravity would cause our bones and muscle to degenerate very quickly. However, would it be feasible if we were able to create our own gravity. If we could spin, the centrifugal force would replace gravity.

That doesn't seem to difficult especially with today's technology. So why isn't it happening?