> Has the manipulation of currencies masked the real changes in our currencies vs gold?
The main currencies (dollar and euro) have been relatively stable to each other and to a basket of commodities, while gold has not. The result is what counts.
As for there being manipulation: Central banks exist to manipulate currency prices to be stable. That is a feature, not a bug - stability is good. But the US Central bank's manipulation has actually had the goal weakening the dollar (by printing more) compared to doing nothing, not strengthening it. There is no reason to believe that the US Central Reserve has been manipulating the US dollar in a dangerous way - if the dollar was to begin falling, it could sell of some of the many assets it has been buying for newly printed dollars, thereby unprinting those dollars again (reducing the money supply), which would make the remaining dollars worth more.
> http://www.indexmundi.com/commodities/?commodity=food-price-index&months=120
On your food price chart: I remember a number of global food crisises caused by crop failures in recent years, such as the drought in Russia. That food prices have been swinging a lot says something about the wheat market, but doesn't necessarity say anything about the dollar. To get a fuller picture of combined dollar price swings, you have to average the price swings of all commodities. Such an averaged price index is called an inflation index, and shows the dollar to be stable (and the price of gold not to be stable).