Can someone explain, maybe in a modern context, what exactly Stalin wanted to achieve and how the world might be today if he succeeded?
If he had been successful in the spread of global Totalitarianism, then what happens? Does he just stay perched on his throne as ruler of the world and live out his life feeling accomplished and that's it?
Or, was he just fueled by a hatred of "free" and capitalist economies where total control was not possible?
Disclaimer: my knowledge of wars (WWII, Cold War) is very weak.
I think the premise of your question is slightly erred.
Unlike other Soviet leaders (such as Trotsky), Stalin believed that the Soviet Union should strengthen itself internally, rather than work to export socialist revolution globally. This doctrine, known as Socialism in one Country, became state policy in 1926.
Whilst the number of socialist states increased in the lead up to and following WW2, coalescing as the Eastern Bloc, the spread of Soviet authority over these states was opportunistic and occurred in two phases. The first phase occurred in 1940 as part of the Soviet-German non-aggression pact (Molotov-Ribbentrop Pact). This saw Soviet troops annex parts of Finland, Romania, and the entirety of the three Baltic states. At the conclusion of the war, those eastern and central states occupied by the the Red Army fell under Soviet influence, comprising Poland, Romania, Hungary, Czechoslovakia, East and East Germany.