I think that the idea of the Party's need for control is absolute. For the Party, the ability to control all aspects of the Oceanian citizens' lives is of vital importance. The Party is only able to be successful when it controls everything in the lives of its inhabitants.
I think that one point to make here would be to include the discussion of technology. The ability to control thoughts and infuse thoughts through "Two Minutes Hate" and other forms of surveillance and mind control are ways in which the Party is able to have a profound impact on the inhabitants of Oceania through control. The Party understands clearly that its success only rests in controlling free will of the people. In being able to use technology in the form of social control and surveillance and being able to ensure that all thoughts are geared towards substantiation of the party, it is able to exercise a great deal of control in the lives of its people.
At the same time, I would suggest that the Party's mechanism of control is seen in the lack of a personal life for its citizens. The Party ensures that they hold complete control over the lives of its citizens in ensuring that there is no private life for them. Everything is public. The outlawing of sex and denial of personal emotions is a way in which the Party is able to ensure it has a large impact on the lives of Oceania citizens. This need for only a public life and never a private one is another way in which the Party ensures that it casts a large impact through controlling the worlds of the citizens of Oceania.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.