Donald “Don” Plaus, a veteran Merrill executive who led the Wall Street firm’s efforts to serve ultrahigh net worth clients and oversaw its private wealth expansion in Florida during the COVID-19 pandemic, is retiring.  Plaus will “continue in his role through March 31 and help to finalize plans for his transition,” a company spokesperson confirmed in an email.  Plaus went from delivering newspapers and working in restaurants as a young man to running a top-tier wealth shop catering to some of the world’s richest families. He spent more than 32 years at Merrill, Andy Sieg, the president of Merrill Wealth Management, said in a statement. Don Plaus, the outgoing head…