looking down the barrel = scavenge the food in desperate hope?

Probably not, the more likely, and more usual reference, is to looking down the barrel of a gun, i.e. disaster and death are staring you in the face.

Thanks

"donor pledges take at least two months to translate into food."

The writer of this sentence must be talking about charities who raise funds for poor and starving people. It means that the Koreans are facing starvation and donations to the charity will take at least two months to reach it's intended recipients in the form of food and other necessities. .