There's nothing wrong with increasing to 9 units if you want to be on the line. But since he only barely saw high blues you have plenty of room to increase by 0.5 units.
As far as what he did almost a month ago on 9.25 units, that's ancient history. Since then he's probably had some glucose toxicity build up, and with an acromegalic cat, dose needs are dynamic as the tumour can pulse up and down. Dose according to the current blood sugar numbers, not worth looking at anything older than 2 weeks old data. The goal is green nadirs and most of his time under renal threshold. He's got a way to go.
It's OK to take a night off from R, that way you get to sleep more.