Hi Reneé...
These are some pretty big topics, but I know from your original post that you are working hard to find the best way to take care of Peanut.
The best place to learn about what you should be feeding your cat, as well as a lot of other good information about diabetes and other aspects of cat health, is Dr Lisa Pierson's
catinfo.org website. She also maintains the most reliable list of the nutritional values for wet foods, a good resource for checking whether a given food is low in carbohydrates. You will see that she is no fan of the "prescription" foods.
One easy choice for wet food, inexpensive and used by many people here, is the Fancy Feast Classic line of patés. All of the Classic flavors are low-carb.
I'm sure you have read that you should try to move away from dry food. The two most common choices for a low-carb kibble are YoungAgain and Dr Elsey's. I think more people are using Dr Elsey's cleanProtein Chicken these days, and some cats tolerate it better than YoungAgain. Dr Elsey's is available both from
the company's website and from Chewy.
Good choices for treats are the freeze-dried meat/fish treats from Orijin and PureBites.