From the way you describe it though, it sounds like his approach life has always worked for him. People rarely change in that situation. So in your shoes I'd be asking myself a) whether according to his values and desires he's sufficiently motivated to make a deep personal change, and b) if not, what relationship structure would work for everybody?
As an example of the latter, if he's not emotionally ready for business partnership, is their a relationship that lets him generate value without messing up the wider system? E.g., what if you were the 51% owner and CEO, with him being Founder and Chief Scientist or some other title that implies prestige but no executive authority? Then you give him an assistant and a series of things to get done so that he can be happy and productive, but he can't actually block the kind of structure you need to run a business at scale.