I have to admit that I didn't notice you were dosing in the am only. I was thinking you were giving .5 2X day. It would certainly be better to dose twice a day. The problem with ProZinc once daily is that it only lasts about 12 hours, and then he is higher the second 12 hours. So you dose in the am, he does okay during the day, skip at night and he is higher during the night and higher the next am. He didn't go too low today; he stayed in very nice safe numbers.
You have a couple choices. You could split your dose and give .25 twice daily. (You have to eyeball half of the .5 which isn't easy. Lots of PZI members use U100 needles and a conversion chart:
Conversion chart Then you can give smaller doses like .1, .2, .4 units. Ideally, it would give him enough insulin overnight to give you an amps of +200, rather than the 300+ you are getting. You could give the .5 twice daily, but it is a little scarier, especially that first dose overnight. (It's harder to monitor at night, though I still thinking staying up all night is overkill.) He should be fine as he didn't go too low today, but since it's early days with the insulin, I would be reluctant to try that until you have some more data. If you give the .25 twice daily for a few cycles and he is higher than you would like, you can always increase by .25 to .5
How about coming over to the PZI forum and geting some advice there? There aren't as many people as here on Health, but everyone uses or has used your insulin. Here is the site:
http://felinediabetes.com/FDMB/viewforum.php?f=24 Just go up to the top of your post and copy the url. Then start a new topic on PZI with a title something like "dosing advice needed" In the box, paste the url from here. That will get everyone up to date on your post.