Several more questions about A Snapshot at the President by O. Henry

Yes, history of George means the history of George Washington.

There is not sufficient context to give an answer to your second question. I would think that the reference is to a bill in the Congress, and that the narrator is suggesting that the support of the President will "kill" the bill. If a bill fails to pass the Congress, it is often said that it died in the House of Representatives, or that it died in the Senate.

Capitol is the word for the building in which a legislature meets. Austin is the capital city of the state of Texas. Saying that he has a boy in Austin just means that the person in question has a son who is presently living in Austin. Saying that he works "around the capitol" literally means that the boy works around the builing in which the Texas legislature meets. Once again, more context might enlighten us, although in this case, i doubt it. (Note the difference--capital means the city which is the general home of the government, capitol is the building in which the legislature meets.)

This is some of the most awful crap i've ever read. I believe that O. Henry was attempting to be clever and to imitate the writing of Samuel Clemens. He fails either to be clever, or to successfully imitate Mr. Clemens, usually considered America's greatest literary humorist. I might understand better if i read the story, but the more short passages of it i see, the less inclined i am to waste my time reading it. Maybe this is an early work of O. Henry, before he developed the skills he showed later.

"He searched his coat pocket, and presently found a piece of paper on which some words were written.
He laid this on his desk and rose to his feet, raised one hand above him, and said in deep tones:
“I die for Free Trade, my country, and—and—all that sort of thing.”
I saw him jerk a string, a camera snapped on another table, taking our picture as we stood.
“Don’t die in the House, Mr. President,” I said.
“Go over into the Senate Chamber.”
“Peace, murand derer!” he said.
“Let your bomb do its deadly work.”

Thank you, Setanta. Sorry for failing to provide a broader context, I just didn't realize this dialogue would have something to do with the bill~~

I have another question. “I think the greatest two speeches I ever heard were his address before the Senate advocating the removal of the tariff on salt and increasing it on chloride of sodium.” What is the difference between "salt" and "chloride of sodium". As far as I know, these two refer to the same thing.

They do refer to the same thing--the implication is that he is "two-faced," a hypocrite and a liar. I suspect that O. Henry, as i said before, was attempting to do satire in the style of Samuel Clemens (also known as Mark Twain). In my never humble opinion, he fails.

Here are some examples of Clemens' wit:

“Get your facts first, then you can distort them as you please.”

“Whenever you find yourself on the side of the majority, it is time to pause and reflect.”

“Sometimes I wonder whether the world is being run by smart people who are putting us on or by imbeciles who really mean it.”

“Suppose you were an idiot and suppose you were a member of Congress. But I repeat myself”.

“A lie can travel halfway around the world while the truth is still putting on its shoes”

The difference between O. Henry and Clemens is that Clemens doesn't try to beat you over the head with his wit, and his wit succeeds because there is so much of the truth in it.