Does 1 Corinthians 7 indicate Paul thought the second coming was imminent?

Yes and he got it wrong. That certainly seems to be the case. It was a common Christian expectation that Jesus was coming back soon until the destruction of the temple in 70 CE (which was after Paul’s death). That’s also why some scholars believe that the gospels were written post-70 (starting with Mark around 70 and then Matthew and Luke around 90 CE), as the church spread and new generations of Christians who didn’t know Jesus or an apostle came on the scene.