1. The name Joe stands for Joseph Stalin who ruled the Soviet Union with an iron fist after world war 2 ended. He also ruled various other Eastern European countries by proxy since he had them work as satellite states. He represents the Soviet Union and all other countries that he had cut off from the remainder of Europe
2. Churchill is looking under the curtain because he wants to get other countries away from the Soviets. He believed that other countries who weren't a part of the soviet union but still were communist countries should be freed from Soviet Union's grasp. It's called an iron curtain because it's a metaphor for strict separation of the two worlds.
3. The primary differences are in the economic model that the two sides employed. West of the curtain there was liberal capitalism while totalitarian communism existed on the other side. The capitalist side was also more liberal when it came to governing those countries as they were mostly democratic, while those east of the curtain had one party systems and were mostly totalitarian.
4. A symbol that can be seen is the background of the eastern part. Unlike in the western part, the eastern part shows heavy industrialization and the world looks dreary, almost like a camp. This is because during the cold war period following world war 2 the Soviets understood that they had to industrialize rapidly in order to catch up to the western world when it came to power and economic prosperity. They focused on heavy industry and in many places the country did look like it looks on the comic.