It's impossible to know what the carb content of this food is without the as-fed values (dry matter analysis). Just because the manufacturer claims that the food is low carb doesn't mean that it is. Most of the grain-free dry foods that use potatoes as the binding agent end up being somewhere around 20-something % carbs (I'm thinking of Taste of the Wild and Blue Buffalo).
There is no "good" dry food for a diabetic cat. Even the lower carb, grain free foods can still keep blood glucose levels high and create problems regulating your cat.
Again, I would really urge you to examine feeding a canned only diet.
Here is an example of an autofeeder that people use to feed canned food when they are gone--you just freeze the food and it stays good for up to 24 hours.
Here is another example of an auto feeder. It has a compartment for an ice pack so that food stays fresh in it even longer. You mentioned that your concern about feeding the canned only diet was because you're often away on the weekends--however, won't someone need to come over and give your cat the insulin injections while you're away? Could this person set the autofeeder when they come to do the injections?
I'm sorry to be nagging about the dry food, but I really just want to help you find a solution that works for you and your cat.