When he acts that way, I'd recommend grabbing the meter and testing him. You will be able to know then what is going on and not just guess whether meds are working or not/whether they are dropping him too low or not/etc. The more often they get tested, the more they get used to it. Trust me ;-) Right now our foster Cecil climbs on top of our foster ChrisFarley purring whenever I am trying to test Chris because we don't test Cecil that much anymore and he is jealous. I am an absolute preacher for testing. Regardless of what meds they are on, the only way to know what is going on is to test. Once you know what is going on you can make informed decisions.
Usually when we get the pens, we still us syringes to draw the insulin out of them. Cats are micro-dosing compared to people so the syringes are easier to use. There is a rubber stopper at the end of the pens. There are a few members now that use the pens with their tips and are doing fine that way too. You just have to do full units I believe, I don't think they do partial units.
Can you spend the next couple of days getting some tests in? Maybe at the time of meds, and another 2-3 others in the day? Maybe we are alarming you for no good reason. Maybe his numbers are looking good and he shouldn't be on meds right now and you can try a food trial. Maybe his numbers are still sky high, maybe they are way too low. A couple days of a few tests could give you an idea of whether he should continue on, switch to shots, or just get off of meds all together for a bit. Personally, I think it would be a good idea to get off of the pills and look at something like Lantus, Levimir, or PZI/Prozinc, but with some data, you may be able to see a clear path on what to do.