This is not a great answer to your question, mainly because I have not followed the tutorial you used and can not help debug it, but: have you tried other more “automated” tools for making sysimages?
I prefer VScode’s plugin for it: Compiling Sysimages · Julia in VS Code
Here I show how it turns TTFX from more than a minute to 3 seconds: Very slow time to first plot, 2022 - #46 by Krastanov