I think you're going to find that the vast majority of us do not feed any dry food...Unless and until the cat absolutely refuses to eat anything else...and there are lots of tricks to convert hard core dry eaters over to only wet.
Pixie will be eating a lot more until he's better regulated. His body can't utilize the calories he's getting properly until then. China used to be eating pretty much every time I saw her...Now she eats probably 1/3 of what she was eating, because her body is able to use the calories better.
There's one dry that a FEW people have used that I've seen talked about some. It's called Young Again Zero Carbs, and is only available online, but like a lot of us, your vet isn't giving you the best advice.
The amount of fiber in dry isn't the important number...it's the amount of carbs. Fiber makes you FEEL full, but isn't much of a food source. I couldn't tell you how many members I've seen who's vet's weren't up to date with the latest treatments for Feline Diabetes. I had to go to three just to find one that would put China on insulin! (and she's acting better than she has in years, peeing a lot less, eating less, playing much more like she used to, and being more loving and friendly. I thought she was just getting old and grumpy, but she's back to the cat I knew years ago...and is Purring more than I ever remember!!
You don't have to spend a fortune on wet food either....The Special Kitty brand at WalMart is cheap and low carb. Friskies pate's are also available in the big cans or the 5.5 oz ones.
Trying to regulate Pixie while on dry food may be a very frustrating thing, and most likely, won't work. I can honestly say I've only seen 1 member who's been able to get their cat off the juice while feeding dry, and that was the Young Again Zero Carb. (it's also very expensive)
We all use the food info listed here to guide us
http://www.catinfo.org/docs/FoodChartPublic9-22-12.pdf
I hope you'll continue experimenting with only wet foods. It really is the best thing for Pixie. Cat's also don't ever drink enough water, so the extra water in wet food helps take the strain off their kidneys (and Chronic Kidney Disease is another complication a lot of times with diabetic cats)
I think as you get him better regulated, his appetite will come down dramatically.
Good luck to you both! This sugardance can be frustrating, but the members here only want the best for your kitty...Nothing else