You may need to ask for medical advice and opinion about your son.
I know of patient's being switched to Novamix to simplify the injection routine but this does not necessaily improve their bsl control according to them and they tend to dgain too much weight.
One thought is asking your son's neurologist whether he woukd benefit seizure-wise from a ketogenic diet, which has been helpful for people with epilepsy.
TIDs have successfully undertaken such diets but his nurse may not be familar with the diet.
With close attention a number of TIDs on a keto diet, not necessarily epileptics but for their own wish to have better BSL control, including fewer hypos appear to do well.
Whether novomix is suitable for such a diet i cannot provide a medical opinion.
but you will note users' concerns above in the second sentence.