You are correct that the meter manufacturers suggest checking with control solution to make sure the meter is working correctly particularly with each new supply of strips. That said, tests with the control solution will only tell you the meter is working with the strips and producing readings within a certain range. It won't tell you anything about the accuracy of the readings you take. It's great to have control solution around to check if one starts getting odd results but I seriously think the recommendation to routinely check is a bit of a marketing ploy on the part of the manufacturers. I have never been able to get control solution at the pharmacy where I bought my human meter and my strips or any other pharmacy I've checked. I can call the company for a bottle and some even provide it gratis but that doesn't help much if I need to test the meter that day. And the few times I've seen control solution available the price is ridiculous and it usually is only good for about 3 months. IMHO I think if it were that critical, the solution would be included with the meter purchase which is usually not the case and the solution would also be easily available at retailers selling the meter.
Interestingly, control solution is included with the AT2 meter and is usually available where you can purchase the AT2 strips but that meter needs to be coded unlike most if not all current human meters. One would think checking might be a way to ensure you had the meter coded correctly but it doesn't because the control solution range for cats is so huge and doesn't differentiate for all the possible codes. Another way to get folks to spend their hard earned money me thinks!
On the AT2 meter, a reading of 68 would be your cue to feed your kitty some food to prevent BG from dropping any lower. 68 is NOT a hypo reading and a non diabetic cat might read lower than 68 on a routine basis. We just don't want to allow our diabetic kitties to drop too low because of the insulin we are giving them. We don't assume a kitty is hypo unless they display physical symptoms including frantic hunger, confusion, staggering, seizures or comatose. We intervene early to prevent hypoglycemic episode.
While a readings in the 300s on any meter (human or pet) are higher than desired, I'd call it high on a pet meter. Your goal with the pet meter is to get kitty into normal range of 68 to about 150 and definitely not over 175. Different animal labs have different highs noted in their normal range.