2: as elevation increases, the number of molecules decreases and the density of air therefore is less, meaning a decrease in air pressure. In fact, while the atmosphere extends more than 15 miles (24 km) up, one half of the air molecules in the atmosphere are contained within the first 18,000 feet (5.6 km).

Because of this decrease in pressure with height, it makes it very hard to compare the air pressure at one location to another, especially when the elevations of each site differ. Therefore, to give meaning to the pressure values observed at each station, we need to convert the station air pressures reading to a value with a common dominator.

The common dominator we use is the sea-level. At observation stations around the world, through a series of calculations, the air pressure reading, regardless of the station elevation, is converted a value that would be observed if that instrument were located at sea level.

3: In the northern Hemisphere the air around a cyclone
(or more commonly called "low pressure areas") rotate counter-clockwise and clockwise in the Southern Hemisphere. They usually bring about clouds and precipitation.

With an Anticyclone
More commonly called a high pressure area the wind blows clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. At the center of the circulation, the air is, sinking air. Generally, this sinking air provides clear skies.

The reason for this for this rotation is due primarily to the Coriolis Effect which is the effect caused by the Earth’s rotation which deflects air moving between two places. It causes an object to move to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

I think the polar front runs from the Bay of Biscay, over the British Islands, to Scandinavia. I believe there is a low center in the Biscay, not far from Nantes, France. There is a high pressure centered over north Italy and I think there is a minor low pressure over the Balearic islands. Now, this is an interesting point.

Sometimes, lows entering the Bay of Biscay, move along the north side of the Pyrenees to end up over the Balearic. Yet you can see that the Spanish Mediterranean coast is clear. That is because the Iberian peninsula is a big high plateau that stops the clouds coming from the west.

My father who was a pilot in the 50s knew that if there were lost over the Med, they should fly toward Alicante because the weather there was always clear. It was the reason that, when retired, my parents moved to that part of the world.

But I digress: this is what I "read" in your map. Perhaps I am wrong, I am not a meteorologist, but I have sailed all around Europe for years and now, I teach meteorology to pilots in Norway.