I'm not in the Dallas area, so can't help with a recommendation, but I can welcome you to the FDMB and give you a little information!
First, I'm happy to hear you've switched to a wet food diet. Do you know if it's also low carb? We like them eating foods that are less than 10% carbs. Here's a
Food Chart that has a lot of the foods available in the US....look in column C for the carb percentage
Next, Vetsulin is really not a good choice for cats...it works much better in dogs but since most vets see a lot more diabetic dogs, they use what they're comfortable using. There are 3 insulins that work well in cats...Lantus, Levemir and ProZinc, so what you might want to do is just call around and "interview" some vets over the phone on what type of insulin they prefer using. As long as you're willing to let them call you back when they have time, most vets will be happy to do it (and if they won't, that's a good indication you might not want them anyway in my opinion)
Vetsulin is a harsh insulin in cats...it goes to work fast, can drop them too low and then wear off before the next shot is due.....Also, if it's dropping him too low, it can trigger what we call a "bounce"....where their body has become used to living at higher numbers, so either going too low, going down quickly or even just going lower than they're used to can cause the liver to release stored sugar and hormones to bring them back up quickly....so it's totally possible for a cat to start in the 400's, drop down into the 40's a few hours later, and be back in the 400's by the next shot time.
One of the other things we're strong proponents for is home testing. Numbers done under stress (like at the vets office) can be effected by stress and be up to 200 points higher than they are at home, so getting a human glucometer and learning how to home test your kitty will be one of the best things you can do for him. Not only will it help keep him safe, but it'll help you to see what's really going on inside his body so you can make changes to dosage as needed.
The people here can help guide you on pretty much everything....but I hope you can find a vet that is willing to give you a prescription for one of the better insulins. Most of us don't see our vets for the diabetes anymore....Only for routine vaccinations and to diagnose other problems.
Do you have any other questions we can help you with?