but he was willing to give the serum to Armin and just about to. So that argument that he thought Armin was more capable and important in the long run doesn't really stand, because if it did, Levi would have done that right then and there. That's what I'm trying to say lmao.

I'm sorry but Eren literally tells him they couldn't have known Floch would show up with Erwin still alive and Levi agrees . It's not my interpretation, it's the literal dialogue in the manga

like this is very ambiguous if you meant to analyse the author's commentary after the scene played out and we had insight in the character's psyche. The future events unfolding and leading to Armin's ultimate role in the story weren't a influence of the characterat that particular time.