This is just little pieces of information that I've pieced together to answer some of the questions you may have.
*Spoiler Alert*
The story of Sonny is as follows. The ZPCI (Zombie Pest Control Inc.) created a disease to infect people and make them into zombies. In return they protect the people and get paid through taxes (which are sky high because of them). Sonny turned into a zombie and died, but was brought back by Louis.
*Possible Spoiler Alert*
I believe Louis is an insurgent. Because in zone2 (Sonny2) when Sonny asks Roald about the tattoos that all the insurgents had, he says they look familiar. Now where could he have seen an insurgent. On the boat! That would also explain why the ZPCI killed him.
When Sonny fights through the ZPCI and makes it too shore (Zone2, Sonny1). You may notice that if you click on the sign it says "80 km to Hew", and in Sonny2, Hew is the final place you visit.
In the first cutscene of Sonny2, if you notice at the very end of it, Felicity is going down an elevator holding a body. If you go to the final cutscene of zone 4, you see that a dead body (the workers brother) is dropped through the top window by Felecity. Finally the workers were fed up and just wanted to bring the mayor down (who was sponsoring the ZPCI).
