I'd hold the 2 units through tonight and tomorrow. The drop from yesterday to today was looking pretty good, and lantus can pull down the numbers even more the next day or two, so if you hold numbers will probably in the good range tomorrow at 2u. Don't worry about the dry food until he's good and clear of ketones, sometimes, if you pull out the carbs too fast, the cat backslides because the appetite isn't 100% yet. Once you do adjust the food, you are probably going to need less insulin too. At this point it's better to focus on good appetite, no ketones, and no symptoms.
So, lets talk about what led up to your cat's DKA, because it's good to identify the triggers. In the past, I've seen 3 major triggers that seem to be the precipitating factors:
1. Acute infection - sometimes there is an infection or illness, and this is the only factor. Sometimes DKA happens for reasons other than infection.
2. Cat is chronically underfed or malnourished - We want our cats on the lowest carb diet we can find and to get the diabetes under control, however, sometimes, it's very easy to accidently underfeed a cat, which leads to fat breakdown, which leads to DKA. If your cat is on the thin side or losing weight, there is a possibility they are not getting enough food overall. Remember, lower carb food is often lower calorie food as well, so they need more of it. In addition to underfeeding, cats can be malnourished for a variety of other reasons - appetite issues, CKD, heart failure, irritable bowel, pancreatitis, etc. Check your cat's weight and body type regularly:
http://www.petmd.com/sites/default/files/nestle_purina_cat_body_condition_chart_crop.jpg
3. Skipping insulin - Vets often advise to hold insulin if appetite is poor. If blood sugars are not low, AND the caregiver is knowledgeable enough to catch and treat low numbers, the advice to hold is not great advice. Often, it's better to shoot a reduced dose, and monitor. Withholding insulin for a diabetic is akin to withholding air for everyone else. A diabetic's body cannot function properly without insulin, as is has many other functions besides lowering blood sugar. Skipping insulin, even for a couple days can be the trigger for DKA.