EEA FP for child over 21

[inczei]

I am a citizen of EEA country, living in the UK with PR document, have a wife from non-EEA country with RC. Her son is over 21 years old and live in his original country. He have hepatitis and very difficult to find a job there, every employee have to apply a medical certificate before apply for a job and in his certificate always there this problem, so no any company accept his application, but of course no-one give a letter about the ground of refusal.
We would like to apply for him an EEA Family permit to come to the UK, work and live with us.
We have tried to apply before and refused as not enough evidence of financial support. We sending money every week to support the family there, but not only for his name, depends who can pick up the money. Totally around £1.000 per month.
My question: how to prove, he need our support? As he have no job, no other income. How much need to show per week or month? Which is better way? Dependant direct family member or extended family member?