Breaking up and postponing the NeuroPsych Assessment was to his detriment. His OT and ST should not have butted in. Breaking up the NPA can enable him to perform much better than doing it all at once. The fatigue factor is reduced. Fatigue is a major factor in his disability.

Reduced function from high to normal does not qualify for disability. Being able to hold a full time minimum wage job means one does not qualify for disability. His career field of choice does not matter with SSDI. If he had private disability insurance, it sometimes does. SSDI is for when the disability prevents any substantial gainful employment (Wages over $1070 per month)

It sounds like he has a good claim for 'pace and persistence' as his main issue. Plus, does he have a difficult time with confrontation ? It is a common symptom. It can make employment difficult.

A report from an occupational psychologist may help.