Hello, I'm sorry to hear of your husband's diagnosis. My brother was diagnosed at the same age as your husband. I'm not a medical professional, just the parent of a kid with diabetes. He's in a phase now where there us a lot going on in his body. He's trying to get rid of all that extra glucose in his blood, his pancreas may have started producing a little insulin yet (that's called a 'honeymoon'), and the insulin levels he's getting are likely to be getting tweaked, as he learns to coordinate the exercise he gets against the number of carbs he consumes, as well as how different foods affect him. So the answer to your question of what you are doing wrong is that you likely aren't doing anything wrong, you just need to get a better handle on diabetes management.
Controlling blood sugar scores is one of the most frustrating things you can do. One day you can have really great scores, and the next you can do the same thing and bounce from highs to lows. My advice is to just keep trying to dial things in as you learn more and more. Keep asking questions like this, keep reading, keep adjusting things as you learn more.
I also take a mixture of Lantus and quick-acting insulin. If his sugars are running consistently high, then he may need to increase his dosage. Give his doctor a call and tell him what patterns you are seeing, and he will work with your husband to get the dosage right. Sometimes it takes some time to stabilize and to know exactly what combination of insulin dosage and foods work best. Each person is different, and of course everything depends on the foods he eats at each meal. I hope both of you have been given training about diet -- what combinations of foods digest quickly and which ones digest slowly, how to count carbohydrates, etc. If not, then you may want to ask his doctor to refer him (and you) to a dietician so you can learn these things.
I personally find that if I eat carbs combined with fats in a late evening meal (after 6 pm), sometimes I am still digesting food when I go to bed and my glucose will have risen during the night. So that may be part of the problem -- the fats slow down the digestive process. Do call his doctor and ask for help. Type 1 diabetes is not a disease whereby the doctor can automatically say, "you need x amount of insulin" -- each person's dosage must be tailored exactly to that particular person, considering their activity, metabolism, and diet. So it probably just isn't quite right yet. Don't lose heart. Adjustments will probably solve the problem.