i'm reading your notes and wondering about using the vet's meter. Was it an Alphatrak? Those are meters made for pets and they read a little higher (somewhere from 18 points to 30%) than human meters. If you are using a human meter (which i think you are) and the vet's meter is for pets, his meter is going to read higher than yours. It's probably going to be less confusing if you just stick with your own meter.
As far as your dose goes, i agree with Dyana. Typically we would say to hold the dose after the first dose reduction and assume that if she went below 50 in the next few cycles, it's the previous dose still causing the low numbers.
But it looks to me like Charlie is mostly flattening out. I'd really encourage you to make certain you get a pm cycle check every evening - she is starting to move down the dosing scale, which is wonderful, but it means you have to be even more aware of her low numbers. And with so many cats having their lowest numbers at night, that makes it even more important.
I think i'd go to 1.0u tonight and try to hold it there for a few cycles, if possible. When cats are going down the dosing scale you have to just follow their lead. If she trends back up, ie, not just a bounce tomorrow or tonight, but in the next couple of days not during a bounce, if her numbers go up, go back up to 1.25u without delaying.
overall, charlie's looking great! congratulations.