Frankly this area could easily be a degree and masters which would still leave gaps. If you read the different forums you will get an insight into the frustrations. Nutrition is a "loaded" area as the official guidelines tends to harm many diabetics via the eat well recommendations; low carb, high fat diets or variants are extremely popular and common sense for many of us, running contrary to what "we" are advised.
Regarding lifestyle many diabetics who are managing their condition educate themselves here, and or get support and answers which helps with lifestyle, reading the forums you will see nothing is off limits. I would like to see Type 1's (and some Type 2's / LADA diabetics) get CGM's or Libre's as these would improve management. I would have thought that further progress would have been made in prevention / management / cure, particularly as many countries have diabetic epidemics and a third of many populations being pre-diabetic. I am disappointed with the big IT companies as they have not delivered on what they talked about years ago - smart watches with glucose monitoring. You will struggle to be a sole source of help, as for example not all diabetics respond to foods in a linear manner, I was diagnosed in Jan 2015 and am still learning almost daily, mainly from the posts here.