Eek, I haven't been checking in for a while, don't like the reds, ewwwwwww!!!! If it were me, here are things I would consider:
- lowering the dose back down a hair and seeing if the numbers improve
- getting a full curve on a night cycle and seeing if that gives you any insight
- trying another insulin - I would try posting in the the L forums, say you have a cat with these somewhat unusual patterns and can't seem to get a consistent response on PZI, and ask for opinions on whether it would be smart or not to give one of the Ls a try - you might find a different insulin works ok 12/12, or I think Lev has some flexibility
It really bothers me that his dose has pretty much doubled since you started the 10/14 experiment, and yet you can only hold good results for a couple days here and there, and then the numbers are creeping back up. On the one hand it suggests you need to be more aggressive with the dose and stay ahead of any temporary insulin resistence, but on the other hand, how far can you keep increasing the dose without starting to wonder if you are on the right track.
Just my musings

I really thought he would be easier to regulate than he has - some cycles are so promising, but then it doesn't seem to stick somehow :YMSIGH: I think it's worth posting in the L forums for thoughts - even if you don't switch insulins, you may get some good ideas or insight. If you do that I'd mention your health issues and difficulty testing at night, b/c that's the first thing they are going to tell you - get more night data! You have some good reasons though that it is tough to do so.