Pre-blood work fasting of about 8 hrs is normal and not usually a problem. And stress OR infection can actually raise blood glucose quite a bit (even more than 100 pts in
some cats). The fructosamine test that you mentioned is the best way to rule out diabetes because it takes an average reading of blood glucose levels over the previous weeks. How long ago was that one done?
What is a little "off" here though is that you say Mikey's
fasting blood glucose reading is normal. I would think that if "white-coat" stress was the issue, it wouldn't matter if he had been fasting or not, it still would have been higher. It could be that infection (or pain) was causing it to rise rather than stress those other times, and that at the time that the fasting blood work was done, either the infection or pain wasn't a factor. Does that make sense? (I'm still drinking my morning coffee, so it's possible that it doesn't).
Anyway, that is something to keep an eye on. As for food, you might want to go back to making your own, although if you can do raw rather than cooked, that would be best. You also don't need to add sweet potatoes or mung beans, except maybe in very small quantities for additional fibre if Mikey has digestive issues. Not sure if you've seen this site:
www.catinfo.org It has excellent info on making your own raw cat food. One caution on the recipe there is that it isn't appropriate for a cat in renal failure because it's quite high in phosphorus. There are modifications that can be made for it to be suitable, or else you could add a phosphorus binder. We can talk about that more later if needed.