Short answers, pulled from the story.
The 93rd United States Congress convened on the 3rd of January 1973. It operated under a unique constitutional arrangement that no other session has ever matched.
Spiro Agnew served as Vice President until the 10th of October 1973. His resignation triggered the first use of the Twenty-fifth Amendment to appoint a successor.
The Endangered Species Act passed the 28th of December 1973. The Safe Drinking Water Act received final approval the 16th of December 1974.
The War Powers Resolution took effect the 7th of November 1973. It limited the president's ability to commit U.S. armed forces abroad without congressional consent.
William B. Saxbe resigned the 3rd of January 1974 to become Attorney General. John P. Saylor died the 28th of October 1973 while serving in the House.