Love Elder Turley
A couple of nights before Jonathan left, he had a night terror (where he has a very vivid dream and while still asleep acts upon it) and felt like Satan was trying to get to him. He actually jumped out of bed and ran downstairs and held the basement door closed so Satan couldn't get him. Will was able to talk to him through the door and help him wake up and come out of it. That is what he is talking about when he said he talked to his MTC President about his night terrors. He also talked to the Stake President about them and when he was set apart, the Stake President told him Satan would not be able to get to him as long as he was a righteous missionary.
As far as the MTC food goes, the MTC in Provo allows you to eat as much as you want, and they have a big selection -- and Jon can put away a lot of food. The MTC in Argentina doesn't allow you to go back for seconds so he was worried he would get enough to eat, but apparently that is not going to be a problem! :)