Summary: Here's everything you must know before Friday's opening bell: China vowed to respond to President Trump's threat to impose a tariff of an additional $100 million on Chinese imports. COO Sheryl Sandberg said Facebook could see a pause in ad sales. JPM executive Matt Zames is reportedly in talks with recruiters about replacing Deutsche Bank's John Cryan. Investors will analyze data from the March jobs report. U.S. stock futures pointed downward on escalated trade war fears.
