Welp. Head teacher always has a chance to do that.
The letter input problem happens to me when working on a language notebook for too long, don't know much else. Skipping last two notebooks is usually better when using Viktor, but still works without.
8 numbers saved before-chase is good, I try and at least get 7 (more if possible) without Viktor. I saw the video, that must've hurt, I died a couple times on final chase for stuff like this. Little things matter.
I know you can do it, eventually, you'll get that perfect run.