I noticed in another post elsewhere on the board your kitty has had some chronic vomiting?
I understand you also feed dry, Since there is really no water in dry food, and cats dont often drink enough on their own, it makes me wonder if she is a little dehydrated (little water intake + vomiting= dehydration)
Add the pooping outside of box and I would suspect there could be some constipation issues going on.
It might be worth calling your vet about this.
LONG before Latte's FD I took her to the vet for the same exact reasons ( vomiting, constipation...going outside box, on dry food diet). Unfortunately we took some wrong steps in diagnosis and tx, leading to more serious issues. For her, they felt it was arthritis and she was having difficulty passing the poop. That is why we tried metacam, which caused kidney failure in her. We also tried a stool softener and had to switch her to wet food so she would get more water. Many years later Latte was diagnosed with IBD/GI lymphoma. I suspect this was really the issue we were dealing with in the beginning, no so much the arthritis. My understanding is that cat's who eat a dry food diet are more prone to IBD, among other diseases. She was 100% dry for 14yrs. The last 4yrs of her life was about 50/50. I was never able to do a complete switch, even with the FD issue due to her lack of appetite. She had to eat something.
I hope this did not sound like a dry food rant. I certainly did not mean it to be. I know you are pretty set, due to your circumstances, not to make the change to wet. BUT, it very well could explain some of the concerns you are expressing from the erratic BG's, vomiting, defecating outside box, etc. I really do think a vet visit would be a good thing so you can address any health issue.
One other thought....do you have any kitty drinking fountains? SOME cats love those. I never had success with Latte...she was scared of them. It may encourage Josie to drink more. If it does not work out, you can return it. No harm, no foul (is that the saying??? :lol: )
I wish you luck and hope things start turning around for the two of you.