Don't you dare suffer for his art. If he wants to suffer for his art, that's fine. It's his life. You can drive him to his gigs, be his sound engineer if you want, and be his biggest fan, but he's got to take on being the damned artist.
Everyday I dread going into work. How do I politely quit my job?
Be the sharper Knife. It's not about what you need to learn. It's about what you already know.
I suggest the problem is not a lack of money or prospects. It's a lack of creativity.