It looks like you've broken through whatever level of glucose toxicity was going on. That impairs the cells' ability to respond properly to insulin. Once the toxicity reduces you will see a reduced need for insulin and doses will have to come down. It's best to have a dose that you can give AM and PM and doesn't result in numerous "no shots". How much to reduce is always a lot of guesswork. I suspect that 2 u will prove to be too low but it's a starting point. If numbers suggest it's too low increase to 2.25 u after 3-4 cycles. Continue those 0.25 u increases every 3-4 cycles until you start to see low blues or high greens near the middle part of the cycle. If you leave the dose too low for too long the glucose toxicity can build up again.
I agree with Kris that 2u is likely too low, but I'm going to suggest an alternative way to approach the dosing. Since your kitty has been up at 4.5u, after this cycle you might try 4u and see if you're able to get two consistent cycles. If you're still having to stall, then try 3.75u, then 3.5u, etc. and work your way down instead of cutting the dose in half and working your way back up. My reasoning for that is that you're monitoring enough that you can keep your cat safe and it avoids leaving him/her high for too many cycles, especially given that he/she (I'm sorry, I don't see a name or gender for your cat) is already getting some pretty high numbers.
I like Djamila's advice - better than mine is. We tend to come at these issues from opposite ends but meet somewhere in the middle. Try 4 u tonight.
I believe Kris and I were both talking about possible options for dosing going forward - not commenting on the dose you had already given. That's why I said, "after this cycle".
