A person close to me had to deal with a concussion for years. Of course each situation is different. Also, I am not a doctor. We know this for a fact, that had he taken less drastic measures after the injury, he would have had to deal with less consequences. Moving, changing doctors, he remained unhappy for long. From what I know, he had far more trouble than you with his first doctor. I personally learnt something from his experience, that when there’s a chance that things can go very very wrong, avoiding or taking actions that would shake the status quo too much is a terrible idea.
The unfortunate fact is the possibility that some part of the cognition takes years to return. He appreciates how he has changed now. It’s been years. I think some of his changes are also due to aging and the hardship. In hindsight, alienating the company might seem like a very terrible idea for him. Fact is, if neither of you were injured, there’d be no such conversations. The core of the problem is the concussion and that is tough to deal with. His was very severe and led to a long pause in his career. As for the doctor, and reiterating that I am not a doctor, my understanding is that there’s little a new doctor can do beyond recommending practice sessions. Unless the science has changed very recently or medical practice is different where you are. Best of luck. Feel free to leave a way so I can contact in case there’s more I can share.