ESA advice urgent need

Hi all, I have posted before but could not find the original post. I am my sons appointee, he is 25 had Adult ADHD along with other mental health issues. We are going through hell with the assessment process. I have tried everything to get him assessed via scrutiny due to his behaviour temper etc, hard to predict as he has no regard for consequences.
Today I took a call form the DWP and was basically told that he will either go to an assessment or his benefits will stop. Despite all the evidence and explanations given to them and the HAAS, the bottom line is " if he can attend his medical appointments and the gym, he can attend an assessment". I was basically called a liar, hot headed, and this lady kind of bribed me into agreeing to another assessment by basically cutting me off every time I objected with "right thats fine, if you are refusing I will make my decision based on what you have just said" I tried to explain that the gym was used therapeutically on his consultants suggestion due to his massive amount of anxious energy and difficult behaviour but got nowhere....she was manipulative and unhelpful. I am at my wits end, my son when under scrutiny is explosive and difficult, he has a speech impediment and stutters horrifically especially in difficult circumstances, he is dyslexic and emotionally immature which is a huge part of ADHD.
ANY ADVICE WOULD BE HUGELY APPRECIATED , can anyone help ?