Congressional staffers were allegedly harassed and propositioned by the lawmakers they worked for — according to secret settlements costing US taxpayers more than $300,000 and preventing the accusers from ever speaking publicly about what they endured, documents viewed by The Post reveal. Rep. Nancy Mace (R-S.C.)  forced out the “slush fund” documents  after obtaining a subpoena voted through by the House Oversight and Government Reform Committee in March. Mace, who has undertaken multiple high profile crusades on behalf of assault victims, opened the files for The Post’s review this week. Neither Congress nor any court substantiated the allegations contained in the files. Rep. Nancy Mace (R-S.C.) pushed a subpoena that brought settlement documents related to alleged sexual harassment by lawmakers to light. Documents reviewed by The Post reveal the emotional toll of the alleged misconduct. Jim Bourg One female aide claimed Rep.…