Well, what would his family do if he hadn't have come here?
Does every family in his country have someone working overseas subsidising them? I'm guessing not, so they're probably doing better than most.
With the cost of living going up phenomenally in the UK, many ex-pats here aren't going to be able to send as much money home as before, if they're still able to send anything.
Most employers do require certificates and grades and qualifications, and if you don't have them, then you will be looked over for all but the most menial jobs.
Remember there are many British people with degrees who can't find the right employer or job and have to make do for a while.
I really don't think getting him English and Maths GCSEs is going to alter anything for you. It's just the way it is, sadly.
Without sounding too harsh, his prospects were always going to be slim. Did he leave his own country to come somewhere safe? Or was it solely economic?
I do think his family asking for constant financial support is also causing him to feel unduly pressured, and also maybe a bit of shame and embarrassment that he can't provide.
The UK isn't the land of milk and honey that some people think it is.