I think you have two issues (let's think of them as opportunities). Food and getting more information. I know you have several cats and have hunted for something to feed everyone. But, if Jack could eat just low carb wet, it might make a huge difference in his levels. I read back over the thread and am not sure if there is a low carb everyone can safely eat? If so, you can leave it out during the day for grazing. If you think one would eat it all, you could freeze it and leave it to thaw so they can only munch. Or use automatic feeders (the cheaper two slot kinds might work for this) and have them open at the same time so everyone has to pick one for a mid day snack. If he gets high carb crunchier, it can raise his numbers by 100+. It also makes it hard for you to figure out how the insulin is really working. I know this is a problem and a pain to try to solve, but it might really make a difference in his levels.
Two, you need more data. The numbers you have gotten show him he drops and maybe fairly low (your 183at +11 makes me wonder how low he was earlier?). So your pre shot reds may all be bounces and the 4 units may mean a lower nadir and bigger bounce daily. That will make it very hard to regulate him. Can you wake up at night and get a number 5-7 hours after the shot? ( If you're anywhere near my age, you're up then anyway.....). Can you get a curve this weekend - every 2-3 hours during the day. That would give you some good information on what is actually happening with the dose.