Hi Josette, I know you said in a previous post that you are uncomfortable with increasing every 3-5 days but I think Oscar will benefit from increasing doses a bit faster than 1 week.
He was switched from Prozinc to Lantus at too low a dose which was held for too long. This has resulted in him staying in higher numbers for many days and it's possible that some glucose toxicity has developed. The term sounds a lot worse than it is, but what it means is that when a cat stays in high numbers for too long, it's body gets used to higher numbers and treats them as normal. It then requires much more insulin to break through to lower numbers.
Would you consider following TR till he starts seeing better numbers so that you can increase faster and get him to a good dose sooner? No pressure. We are here to help whatever you decide to do.