Insulin and ketones can make the potassium really low. That's what probably led to the constipation/nausea. When potassium is low, muscles are unable to contract and become flacid. This includes the muscles of the intestines. Sometimes, oral potassium isn't absorbed efficiently for whatever reason, and supplements have to be increased. Labs should be drawn regularly when on potassium anyway, because elevated levels aren't good either.
It's great that he's eating well and no ketones and nausea is gone! Adding water to food will help dehydration, and getting sugars lower will definitely help. On your spreadsheet, it does look like the insulin is doing something. That is, your numbers at +4 to +7 have been lower than the preshot for a lot of the days. That's good. He's been at the dose for 6 cycles, so you can increase when you feel comfortable doing that.
Don't feel bad about taking some you time. It's a balance having a cat that needs daily care, and yet being able to do the things that are important to you. I've missed all my vacations this year, cause I was too afraid to leave. But now I found a boarding vet that will provide care. It sounds like you have a good system.
I'd continue to increase by the 0.5U. Sometimes, the day after the increase, blood sugars are a little random. That's why the 6 cycles is important, especially with the depot insulin. 0.25 increases is too low at this point with the history, dehydration, and such high sugars. Your dose is probably above the 5U you were at before and the sooner you get him there, the better. Once you start seeing better numbers (more yellows), then 0.25 increases might be better.
