Short answers, pulled from the story.
The 93rd United States Congress met from the 3rd of January 1973 to the 3rd of January 1975. It covered the last 18 months of Richard Nixon's presidency and the first 6 months of Gerald Ford's presidency.
The 93rd Congress had three Senate presidents because Vice President Spiro Agnew resigned on the 10th of October 1973, Gerald Ford was confirmed as vice president on the 6th of December 1973 and later became president on the 9th of August 1974 after Nixon's resignation, and Nelson Rockefeller was then appointed and inaugurated on the 19th of December 1974. No other Congress before or since has had more than two Senate presidents.
The 93rd Congress passed the Endangered Species Act and the Comprehensive Employment and Training Act on the 28th of December 1973, the War Powers Resolution on the 7th of November 1973, the Employee Retirement Income Security Act (ERISA) on the 2nd of September 1974, the Safe Drinking Water Act on the 16th of December 1974, the Equal Credit Opportunity Act on the 28th of October 1974, and the Privacy Act of 1974 on the 31st of December 1974, among many others.
The Senate Select Committee on Presidential Campaign Activities, chaired by Senator Sam Ervin, opened its Watergate hearings on the 17th of May 1973. The Saturday Night Massacre occurred on the 20th of October 1973, and impeachment proceedings against Nixon were initiated on the 30th of October 1973. The House Judiciary Committee began impeachment hearings on the 9th of May 1974. Nixon resigned on the 9th of August 1974 before a full House vote could take place.
The War Powers Resolution was passed on the 7th of November 1973. It asserted that Congress held authority over the commitment of American military forces abroad, limiting the president's unilateral power to wage war. The Case-Church Amendment, passed on the 1st of July 1973, had already cut off funding for military operations in Cambodia and Laos.
Senate Majority Leader was Mike Mansfield of Montana, with Robert Byrd serving as Majority Whip. The House was led by Speaker Carl Albert of Oklahoma and Majority Leader Tip O'Neill of Massachusetts. Senate Minority Leader was Hugh Scott of Pennsylvania, while Gerald Ford served as House Minority Leader until he resigned on the 6th of December 1973 to become vice president, when John Jacob Rhodes of Arizona succeeded him.