NEW YORK—Wall Street ended firmer on Wednesday in a partial rebound from the previous day’s broad sell-off, with remarks from Federal Reserve Chairman Jerome Powell and the ongoing debt ceiling debate keeping a lid on gains. The S&P 500 index and the Dow Jones Industrial Average advanced, but the Nasdaq Composite closed lower as Treasury yields halted their ascent. Defensive sectors took the lead as investors sought stability in the volatile market. All three remain on course to post monthly declines, with the bellwether S&P 500 snapping a seven-month winning streak. “The same story we’ve seen for a couple of weeks,” said Oliver Pursche, senior vice president at Wealthspire Advisors, in New York. “Investors are concerned about three things: the eventual taper of bond purchases by the Fed, ongoing inflation with Chairman Powell saying it’s going to stick around longer than initially expected, and the debt ceiling issue that congress …