Thanks, Julia! He's about a half pound overweight. Maybe. Not too much. He's not exercising as much as he used to--probably cause of the all the adjustments his body's been going through, his age and his hyperglycemia.
He's eating (roughly) the amount he should each day (yesterday he ate less, today he'll probably eat more--which is normal for him). Today I didn't give him much lunch just to get him adjusted to the two bigger meals (if he goes to insulin or not, I'm aiming for a larger breakfast/dinner--when he'd hypothetically have insulin--and two smaller snacks).
On the positive side, so far the urine is testing negative for ketones and glucose (though I wonder if it's too dilute). Do you know how long I can wait after he's urinated to test? I know when I go the doctor and give a urine sample, they typically don't test it for many hours (at least) after. Does the same hold true for cats? I got him the Tidy Cats Breeze litter system which is GREAT, btw--instead of using the pads below, a tray just collects urine and I empty it in the toilet and wash it after. No smell and he loves it.
I wouldn't worry about focusing on excercise to lose weight (especially if he's an older, indoor cat). You'll want to focus mainly on diet and making sure he's eating the right amount to maintain a good weight. Don't get me wrong, excercise is great and you should engage and play with him as much as he allows you to, but as a weight loss measure, it's not going to be enough for an older cat.
If he doesn't have glucose in his urine, that's great, and a very good sign. Diabetic cats don't have glucose in their urine until their BG reaches the renal threshold (the point with high BG where their kidneys start to spill it into the urine), which can be anywhere between 180-250 depending on the cat.
I have three Breeze boxes in my house, and I love them! I've been using them for about 5 years now. So much easier than regular litter, and so much less waste. And yes, easy to get a urine sample if you take the pad out for a bit. However, I don't think you'll need to worry about ketones really if his BG is testing at home in a normal-normal high range, as you're suspecting.
We found that the pellets tended to stick to the cat's poo too much to flush down the toilet unless we waited a day to let it dry out. This wasn't an issue in the old place when the litter boxes were in the basement and the downstairs half bath so we didn't mind waiting to scoop it out, but was a huge issue in our current place where the boxes are in our only bathroom, the bedroom, and off to the side of the downstairs dining room. Needless to say, we scoop immediately now, and we don't like to flush the pellets so we use a couple
litter genies, and they work awesome. No smell at all.
The other thing you'll find is that if your cat ever has a case of runny poo, the pellets are absolutely the worst thing ever. If you find yourself in that situation, you can swap out the clay Breeze pellets and pad for some Feline Pine pellets. The pine turns to sawdust with the urine and you can sift it down into the tray and empty it (and it's compostable), and poop is very easy to scoop out, and you don't have to worry about wasting the pellets because they're pretty cheap. I've had to do the switch with the litter boxes a few times when Bandit had IBD flares and when Orpheus first came home to live with us, and it's pretty painless. After Bandit's issues in March, I just left the downstairs box full of the Feline Pine because it's not that much less convenient than the Breeze Pellets (I have to empty the tray 2-3 times a week instead of once, but you don't really ever have to change the pellets out unless you need to clean the box), and it's nice to have the extra option there. The cats use both of them (although Bandit seems to prefer the pine downstairs, and Orpheus the Breeze boxes upstairs, but that could also just be that they prefer those specific litter box locations).