Bringing up Cambodia and forcibly removing religion, there isn't a one-step cure. There is no one thing someone can do. Obama, the most powerful person on the planet, couldn't get medicaid through without weakening it considerably. Even if someone had the power forcing sudden change on people doesn't tend to go down that well. eg Making homosexuality and gay marriage legal for anyone 16 plus in 1960 may have had repercussions. Instead we had incremental change leading to where we are now. Fairly peaceably.
On the subject of corporate power v people power I think this is one of the main issues. We don't just involve ourselves in other sovereign states at the point war is imminent. Western policies and actions have been involved behind the scenes for a long time propping up dictators etc to serve business interests.
People before profit. I'm amazed at what conditions we are expected to swallow for the benefit of 'the market'. The market is a non-sentient being. What is in the interests of 'the market' is against the interests of all but a very tiny number of people.
The EU are looking to bring in TTIP (Transatlantic Trade and Investment Partnership) ostensibly to improve trade between America and here and make us all rich! This will give corporations more power in comparison to governments. One thing you could do is support opposing that. It will reduce workers rights and force govts to privatise public entities even if they don't want to. Similar agreements (Trans Pacific) saw the Australian govt. successfully sued by Philip Rothman for reduction in profits when the brought in a policy to make cigarette packets plain. So, for instance, if the UK govt decided to make fracking illegal, oil companies could sue the UK for billions in lost potential profits under the TTIP agreement as proposed.
I said I didn't have answers but one thing you could do is join a union and encourage others to do likewise. Unionised workplaces usually have better terms and conditions and are more likely to get (bigger) pay rises. this could help keep income differentials more equal.
One thing to think about is that politically you (I'm assuming you're not closely related to the queen, Bill Gates or a cabinet member) and I have more in common with the 99% across the world than we do with the 1% in this country.
I disagree that we are over-populated and unless you are sanctioning killing off the majority of North Americans and Europeans it's a moot point at this time. A more equitable educated global population would probably see a drop in population growth anyway.