If 8 and 8 works for you most of the time for insulin shots, then I'd go with that. There are always going to be days here and there where things have to be changed - you do have options with those. If your schedule is reasonably flexible, you can cover a late shot by doing 2 shots 18 hours apart instead of 12. Or if you can shoot at 11 again the following morning, you can work the time back gradually to 8 by 15 minutes per shot. The other option is to skip Sunday night's shot entirely. A lot depends on your schedule over the following few days, but a lot of us have had to skip an occasional shot due to prior arrangements and most cats get back on track after that really quickly.
You can absolutely feed all the cats the same food - it is definitely healthy for all of them. Time to debunk a few food myths I think!!
Most vets are not dietitians. So they're as prone to falling for the hard-sell from the prescription food companies as anyone else. My vet said they were going to ask "their" dietitian about food for Rosa and then recommended the Hills diabetic diet. When I questioned them a bit further, I found out that "their" dietitian is actually the dietitian at Hills Science - I think this is a common problem. What else were they going to recommend except their ridiculously priced (and too high in carbs) prescription food?
People, including vets (and on this I think they should know better) are often put off by there being meat by-products and organ meat in the commercial cat food. But that's our "icky" factor kicking in - cats are designed to eat the whole of their prey - fur, skin, bones, organs...the whole lot. So finding there is organ meat or skin in a commercial cat food might be off-putting to us but it is exactly what a cat needs! And that goes for all cats, not just diabetic cats.
We switched all of our cats over (apart from our housemate's 2 - he refuses to switch away from dry food and I can't really control that) to Friskies. That included taking our CKD kitty off her prescription food (which she hated anyway - she'd steal anything she could rather than eat it) as well. They're all doing really well on it - more energy, better fur condition. And our CKD kitty's recent bloodwork came back better than ever!! There are some people on here I think who use the prescription diets, but most of us don't - they're too expensive and they just don't work any better (and maybe not even as well) as the commercial food as long as you buy the low carb versions.
The Alphatrak is a crazy price and isn't going to do a better job than one of the cheaper human glucometers. There is a difference in the readings from the 2 (the human glucometer will read a bit lower), but it's like comparing Celsius and Fahrenheit - both are right, you just have to know which one you're working with! You, as so many of us have, will do just as well with one of the ReliOn meters or similar. My ReliOn Confirm cost around $16 and the test strips come in around $40 for 100 - and you can buy them at a discount online from ADW too. If I remember right, the ReliOn Prime costs about $1 more for the meter, but the strips are cheaper so you might want to see what your local Walmart has and work out which one you think you want to use.
I'm glad you've been able to figure out which syringes to buy - it's not always easy to know, so please keep asking questions whenever there's anything you're not sure about!
Diabetes isn't a diagnosis any of us would want to hear, but please be assured that it is manageable and Buddha can still have a long and happy life with you helping him by keeping his condition under control. 
Ack, I sent you the link to the Canadian Accu Chek website, I`m sure the U.S. has the same deal...but if not, you might want to pop across the border and pick one up (assuming you choose to get an Accu Chek) -- and you`ll get it cheaper than I did because your $ is worth more up here.