On the food, many people free feed or give small meals throughout the day. I see it advised to not feed for the last 2 hours before you test and give a shot, to avoid a food spike affecting the ps#s. Other than that, I agree with feeding an unregulated diabetic cat as much as they will eat! They aren't able to use all of the food, so they eat more to compensate. Do you weigh Blackie? I try to weigh Tinkles weekly to see how much he gains or loses. It's another indicator of how well the kitty is responding to treatment.
Just to give a comparison, I was feeding Tinkles 4 or more cans of FF a day when he had really high #s all of the time. Once he got down into better numbers, he slowed down his food intake to about 3 cans. Remember, ECID though...I'm not saying you need to feed Blackie 4 cans a day! I can't free feed, so I give two large meals and a snack (or two) in the middle of the day.