Was the king leaning on him?
Rashi: He leaned on him yesterday, in Elisha's house.
Why did the king appoint him to stand in the gate?
Malbim: The king appointed him to prevent people from taking spoils for themselves 1 . The spoils belong to the king's storehouse!
How could one guard stop everyone? (a) Surely many people were close to death and too weak to go to the camp, and their family raced back to bring food to them. (b) After such terrible hunger, prices would not plummet so much if everyone took back only as much as food as he could carry at once. Surely most people raced to deposit in their houses, and return to the camp to take more! Perhaps the king appointed many servants to stop people; the verse mentions only the Shelish, to teach how Elisha's words were fulfilled. However, Malbim implies unlike this. Refer to 7:18:1:2 and the note there. (PF)
Why does it say "Ka'asher Diber Ish ha'Elokim? Verse 16 said "ki'Dvar Hashem"!
Malbim: Elisha said on his own that the man will be trampled 1 . Hashem did not say so.