“He is hoping to miss no more than six weeks of performances, returning for a late-March run in the title role of ‘Simon Boccanegra’ at the Staatsoper Unter den Linden in Berlin, said the spokeswoman, Nancy Seltzer. … Mr. Domingo, 69, suffered ‘intense pain and discomfort’ while singing and conducting in Tokyo [last week], Ms. Seltzer said. “