Hi Gabrielle! Welcome to the Lantus forum. I'm so sorry that your kitty has acromegaly, but Wendy is one of the moderators here and she has a lot of experience with it. We have several other members whose cats are acrokitties or whose cats are getting high doses of insulin, so you've found a really good community of kind and generous people.
One of the most important bits of advice given to new members here is to start your cat on low carb wet food. This change alone often helps cats into diabetic remission. My cat also has kidney disease in addition to her diabetes and her kidney disease is now diet controlled without resorting to prescription or commercial high carbohydrate renal diets. Many caregivers here feed their CKD cats foods from Weruva and Soulistic, both of which you can get at Petco, and many of them are low in phosphorus. You can also get phosphorus binders to add to low carb food. My cat also has gastrointestinal disease, so I've opted to feed her a low carb, low phosphorus raw diet that has lowered all of her kidney values dramatically in a matter of 6 months. I know this is not necessarily in the cards for all kitties, especially acrokitties, so it's a question of experimenting to see what works.
Since you're already working with an internal medicine specialist I'm sure you've gone through the options of how to manage Max's diet, but both the diabetes and the kidney disease can be managed with low carb food without privileging one condition over another.
Another important aspect of how we manage insulin dosing and low glucose events is through the feeding of a combination of low carb, medium carb, and high carb foods. Having these different combinations of carb content on hand helps us help you steer Max's glucose levels so that he can get the most insulin in him while also keeping him safe. Once you get a handle on how the forum works, you'll be able to understand a bit better how it all works.
Hang in there, and let us know if you have any questions or need more help.