Nice yellows today! I really think you need to consider the switch when this bottle is done since, like Julie said, the Prozinc doesn't seem to be lasting long enough. The switch may help push him out of any insulin resistance he has. Lantus is a bit cheaper than Lev, and while it can sting, it doesn't sting all cats, so maybe you can start there. You mentioned a friend that had a script you could get some from, or if you look around some pharmacies will sell a single pen for you to try. Then if it doesn't seem to sting you could buy from Canada. Maybe that's all he needs, but if not then you could get the tests done.
ETA Another reason to maybe try Lantus first is the patent is about to run out and there will be cheaper generics available soon