The thing with Pip and being ND I can almost guarantee that unless you understand the nuances in the questions then you get refused.
There is a poster on tik tok who goes through the questions and explains everything (think in RL she is a solicitor)
He should apply again taking her advice and relating it to how he lives.
Could you approach this as, if he can put aside the fact he doesn’t believe he has ADHD and autism and “play the game” it will mean he gets more money in and that will mean he can find a better flat/car/wont have trouble with his bills/can afford stuff etc
If he has a diagnosis of ADHD then meds are what he needs. Some people might get results from things you can get online or OTC eg, Lions Mane, L Carnitane, Saffron, etc but meds are what he needs (I take meds and all of the above and still my brain doesn't quieten but I can get stuff done)
Could you maybe give him the information that having ADHD means not only is his brain a different shape to a NT person but if he goes through life unmedicated his lifespan will be shortened by about 15 years compared to a NT person
If the first meds he gets don’t make him feel right then he can try others. There are different brands, different strengths and different types
He does need to try them for at least a month to get used to them and then he can try stronger or a different medication. He needs to go back to the psychiatrist who diagnosed him and go through titration.
Maybe point out that the way he is with people and the mess and the destruction are all part of his ND and if he still thinks he is not ND then he needs to look at how NT’s live.
The anxiety and frustration that comes with being ND in a NT world manifests as anger.
Being ND and not being able to concentrate on anything that doesn’t interest you when surrounded by people where life, living and the right words comes easy to them even if it is the most boring thing in the world is like a bad joke.
He is probably a much more intelligent guy than his fellow co workers so seeing people progress above him is really frustrating
I also have a DS diagnosed with ADHD and is more than likely ASD but hasn’t gone for a diagnosis. He is medicated
School wrote him off as never being able to be a functioning member of society and able to look after himself let alone get a job.
Within 3 years of him being diagnosed and medicated he has a managerial role, his own start up business and is learning his 3rd language
Ds never believed he had ADHD and was resistant to meds but he can see now the difference they make.