This is the tricky part. Too much insulin can also look like too little insulin, and both can show high numbers. However, if you've safely increased the dose according to the protocol - which you have - then it's not too much insulin. We'll typically see too high a dose when people have been given too high a starting dose by their vet, or if they have increased faster or by larger increments that what is in the protocol.
Cleo has been on this dose for over 6 cycles with only yellow nadirs. So you could increase to 2.25 units anytime. And Marilyn is right, Cleo is bouncing from those yellows. It's very frustrating, I've been there too.