Hi Erin and welcome!
I don’t know that I agree with your vet about feeding. Dogs do fine with 2 meals a day but cats not so much. What kind of food are you feeding him? We try to stay away from dry food because it’s high on carbs. I personally feed Minnie, who is also on Lantus, small meals several times a day with the bigger meals being around shot time. And the Lantus injections should be 12 hours apart, not at meat time. Is that what you’re doing? I askbecause I had a very bad vet at first that told me I didn’t have to space out the injections every 12 hours and that was completely immaculate. I only found out weeks later. Anyway, there are some tips on doing the injections and if you’re going to home test on that as well. In the meantime, take a look at this link so you can help us help you:
http://www.felinediabetes.com/FDMB/threads/new-how-you-can-help-us-help-you.216696/
there are a lot of people more experienced than me her and they’ll chime in as well. Hang one and welcome again!!