NEWYou can now listen to Fox News articles! EXCLUSIVE: Three members of Congress representing heavily Cuban-American districts are demanding the Trump administration shut off the remaining commercial “valves” of support for the communist Castro and Díaz-Canel regime in Havana after effectively blockading key oil imports in recent days.The demand from Reps. Carlos Giménez, Mario Díaz-Balart and María Elvira Salazar, all Republicans from Florida, comes as Cuban despot Miguel Díaz-Canel warned his country is “close to failing,” according to German outlet Deutsche Welle.  Díaz-Canel also warned oil supplies may run out within 15 days amid the threat of U.S. tariffs on…