The social contract is within the state of nature, in that humans will only tolerate so much injustice or tyranny before revolution is imminent. John Locke suggested that humans had a right to remove their government, by force if necessary, if that injustice became too great.
The problem is that such a threshold is inevitably high, as a decision that a government is hopeless and to take the personal, political and human risks associated with revolution is many times a life or death scenario. Humans will endure a lot of injustice before taking such risks, and this leaves government with a lot of latitude for tyranny.
I think you are referring in your first post to the idea that people will act in their own best interest, and the government exists to look out for the interest of the populace as a whole. In your last post you mention consent to be governed. This is the idea that the government should be of the people and by the people, as our founding fathers designed it. This means that people are governed because they consent to be governed.
I have to agree with #3 on this one. You need to really specify which particular approach to the "state of nature" you are referring to and which kind of "political society" you mean. How you answer those questions will greatly affect your overall response.
I am assuming that you are making reference to Rousseau's theory of the "noble savage." Enotes has an excellent resource that addresses Rousseau's work on this topic at http://www.enotes.com/discourse-origin-inequality-salem/discourse-origin-inequality.
The "state of nature" is the notion that humankind exists (ideally, according to the Romantics) in nature and that any sort of government imposes unnatural rules on human behavior. The corollary belief is that the absence of government, laws, and rules allows humans to achieve their fullest potential. These beliefs presume that humans will of course behave altruistically, or at least not rob and kill each other.
Life in a "state of nature" is a utopian idea that would never work in practice, due to the reality that not every human being is willing to behave in a moral or ethical way without being compelled to do so by fear of imprisonment.
John Locke with concen to "consent to be governed".