By Stan Choe | Associated Press NEW YORK — The U.S. stock market’s sell-off is worsening Monday as Wall Street questions how much pain President Donald Trump is willing for the economy to endure in order to get what he wants. The S&P 500 was down 2.8% in afternoon trading, coming off its worst week since September. The Dow Jones Industrial Average was down 838 points, or 2%, as of 2:04 p.m. EDT, and the Nasdaq composite was 4.3% lower. RELATED: Tesla shares plummet as Wall Street rethinks sales projections The main measure of the U.S. stock market is on...