I implemented Dave's Change #2 first, as it was the easiest to do. 

• I first set up a child theme to Retrospect, as described in the WordPress support docs. Files and settings in the child theme override those in the parent theme, and all of my changes will be in one place. The child theme is on GitHub at https://github.com/scotthansonde/wordlandBaseline
• I copied over the parts/footer.html file from the parent theme folder to the child theme folder.
• I edited the text as requested. The footer now reads "Written in WordLand, running on the WordPress platform."

Update

• Corrected the text and changed the text to black (using theme-5 instead of theme-3 in footer.html)