Any reference to "6-12-12" refers to Dr. B's central diet recommendations, 30 g of carbs/day, split into 6-12-12 over breakfast, lunch and dinner respectively. i would really recommend that you obtain and carefully read the book, "Diabetes Solution." Few endos will have the same view of diabetes that Dr. B does. Many endo's think it is just fine to shoot up to 2-300 mg/dl after a meal as long as you come down later and they think an A1c of 7% is absolutely great. Not Dr. B. He believes that we have a right to a "normal" blood sugar which almost never goes over 140 mg/dl and our A1c should be less than 5%. So you need to decide what your goal is. If it is to normalize your son's blood sugar and extend his honeymoon potentially forever, then don't just accept the endo's targets. Make your own decision.
That being said, if you read the book, it will describe a basal/bolus regime. A basal regime is the amount of insulin required to keep your blood sugar flat and normal (83 mg/dl) when you are fasting. By fasting, I mean not eating for a while. So if your son is having to eat so he doesn't go low on his current Lantus level that indicates that his basal is too high. Waking up at 120 mg/dl is still high. It happens when you have diabetes, as Sheila indicated, it is called Darn Phenomenon. If you were Dr. B's patient, he would have you take insulin to address the morning high.
So again. Please obtain and read the book. It is at most public libraries. And the situation you describe suggests that your son is getting too much basal.