When and where are we exposed to most cosmic radiation? I understand the mechanical dynamics of being faced away from the Sun at night, having a lower altitude, not being in the weak points at the poles in the atmosphere, being in a valley and others decreasing cosmic radiation.

Are the particular areas on Earth where cosmic radiation is amplified or unprotected by the magnetosphere because of the  lensing effect on cosmic rays either by location or angle of the sun?
You seem to have a good understanding of cosmic rays, but not all of them come from the sun, so there will still be some coming in at night. These will tend to be the most energetic ones emitted from supernovae and other violent cosmic events. You are most at risk on a long distance airliner, which flies at abut 33,000 feet, but the risk is small and nothing to get worried about. For airliner crew it is more serious, but for the vast majority the time spent at 30,000 feet doesn't seriously affect their health, otherwise they'd be getting danger money. If you want to avoid dangerous radiation, the thing to worry about is radon gas. This is emitted by the decay of uranium in granite rocks. Radon is an alpha emitter, and is dangerous when inhaled or ingested. You can find a map on the internet giving radon levels in your area (they are very variable). If you are in a high radon area, put a gas proof covering on your ground floor and make sure your house is well ventilated. In some houses, radioactivity can reach levels which would be unacceptable in a nuclear power station or research establishment. I don't know of any place on Earth which is especially safe from cosmic radiation except, perhaps, a coal mine or a nuclear bunker.