Hey, I am not sure if I can help in any way, but I was pretty much the same as this between the ages of 19-24, and I managed to get myself out of the dark situation I was in.
The whole turning point was finding something I was actually interested and getting some self worth from it.
I have a bit of advice that might not change things overnight, but you mentioned he is a great cook. Have he considered blogging? Although it won't make him money overnight, he could write a blog about some great recipes. Use a video and then start talking to other bloggers in food etc.
After doing this for a while, not only can it improve his self esteem, but it can also lead to a decent advertising income. For a Youtube video, you get about £1 per 1000 views, and you can sell advertising space on a website for some good money. If he has a back condition, being able to work from home means he can make sure he isn't rushed off his feet all night.
I've gone on to be quite accomplished in my industry, and would be more than happy to give some tips based on how to get started - and the beauty of it is that it's cheap as chips.
feel free to email me if you think I could help. I'm not advertising on here as my advice is completely free. I'd just like to help someone who is in a similar position as I was.