I would suggest using the human meter for regular testing. Our protocols are written based on the readings from human meters, so the stickies will make more sense for you and Bundy's patterns are likely to be easier to interpret if you go with that. Of course we can work with whatever you prefer, that's just my 2 cents.
As for shooting early, the problem with shooting at +10, is that then you have to wait 14 hours for the next shot in order to keep on your 12/12 schedule. And it's hard enough to wait 12 hours, let alone 14! The other option is that you keep shooting every ten hours, but then your shot time is constantly changing which means sometimes you're getting up in the middle of the night to shoot, and it's hard to plan your life around a moving shot time.
If you are consistently home every eight hours, every day, we can talk you through TID dosing, but as Kris said, it is
very difficult to sustain since you need to be able to monitor each cycle so you can't leave the house much and your sleep gets interrupted. It's up to you though, some people have done it.
I think a better plan right now would to go with your plan of choosing one meter and using it first every single time so we have one cohesive picture. Then be aggressive with the dose increases - keep increasing every 4th cycle and make sure you keep monitoring the PM cycle so we can know that he's still safe. And finally, be absolutely positively certain that he is eating a low carb, complete diet, no carb treats, and no access to any other food from other pets in the house.
If he'll eat raw turkey, consider adding FoodFurLife supplement powder to make it a complete food and feed him that. Then you know it's low carb and has all the nutrients he needs.
Getting his numbers under control will go a long way to helping him gain back some of that weight.