Short answers, pulled from the story.
NASA headquarters established the Apollo Applications Program in 1966 to keep its workforce employed after the Moon landing. Wernher von Braun led the Marshall Space Flight Center and pushed for a smaller space station to provide work beyond Saturn rocket development.
Fiscal Year 1967 allocated only $80 million against an estimated need of $450 million. Over $1 billion was required just for the following year before budget constraints hit hard when the Johnson Administration rejected full funding.
A Manned Venus Flyby plan used the Saturn S-IVB stage as a wet workshop for three men. Astronauts would live inside empty fuel tanks after venting remaining propellant to space and separated from the stage shortly before reentry on their return to Earth.
Contractors like Boeing, Grumman, North American Aviation, and Rockwell hoped to delay staff reductions when NASA shifted focus after procurement of extra Saturn Vs stopped in 1968. Three proposals emerged including an Apollo Telescope Mission using a modified Lunar Module ascent stage.
The Apollo Spacecraft filled with toxic gas but the crew survived upon landing after conducting rendezvous and docking exercises with Soviet Soyuz 19. Thomas P. Stafford, Vance D. Brand, and Donald K. Deke Slayton commanded the mission that marked the diplomatic conclusion to the era.