Ehm, I said I think that Samuels is the character you might be looking for, somebody through whom the end of Terra Prime is symbolized. That's not putting words in your mouth, it is just a guess. And I obviously have to guess as you never say concretely how you want the end of Terra Prime to be dramatically shown. For me as well as most other folks the death of the villain plus Samuels conversion is really enough to symbolize that "the demons of our past are conquered (for now)".
I would never insult you but the activity you engage in, hyperliteral reading and plot hole buggery, is obviously pretty stupid. Not seeing the forest because of the trees and so on. You could take the greatest stories of the world and find dozens of plot holes. It is just a pointless activity and the wrong approach to any kind of fiction.
Because, to repeat myself, fiction means making stuff up. This automatically involves leaving things out. Even if you are Tolkien and devote a big part of your life to create an entire fictional world it will be full of "plot holes".
Anyway, back to the actual story. Would you mind to point out HOW you want the end of Terra Prime to be symbolized? In my eyes we have the death of the villain, Samuels conversion plus Archer's speech that symbolize it in the actual episode.