Hi Jamie. Sorry to hear about the poor situation of your friend.
I feel I can offer some advice. Unfortunately I can’t help with the symptoms he experiences, however, in terms of quality of life and management of symptoms your friend needs to see a Specialist Neuro Rehab Occupational Therapist.
The bread and butter of the OT is to maximise the engagement of their clients in meaningful activity, thus improving quality of life, and hopefully, as a consequence, improving mental health.
They will support them to manage their pain and fatigue on a daily basis so that this barrier to meaningful activity is reduced. As a specialist in neuro rehab they will also be able to address his cognitive issues and will be able to provide strategies etc that again, will reduce this barrier to engagement in meaningful activity.
They OT will start small and begin with simple achievable goals, potentially working up to return to employment etc.
However, as he is 5 years post injury, he will likely not be able to access statutory services, but it will always be worth a phonecall with his local community or inpatient neuro rehab service to speak to an OT there.
The only option would be to go privately, and I appreciate there is a cost to this.
But what price do you pay for an improved quality of life?