OMG. The worst thing you can do is quit your job and care for him like he is a small child. he has a NonVerbal Learning Disorder (NVLD) (like me...I have a very bad one...verbal 120 and performance 85). Yes, I am disorganized. Thankfully I was taught to use post its, a bulletin board and my phone and he can learn these coping skills too. I also grew up very depressed. It took me a long time to find the right medication, and I was medication sensitive too, but I never stopped trying and I never quit therapy and I'm really a happy person today. Do not let him give up on himself by admitting to him that, yes, he is a total invalid. He's not. These are not the worst things an adult can have and they can be greatly helped. He should NOT refuse to go to work due to depression and anxiety. I understand. There were days I was terrified I'd have a panic attack and go crazy in a store or in front of my co-workers, but I pushed. I did not substance abuse either. I had a hard time getting out of bed sometimes, but I kept and kept going for help. I would not give up on me, but I may have if my mom would have taken care of me like I was ten years old. She didn't. She had no pity. It was for the best that she made me stand on my own or I wouldn't be where I am today. My mom was mean and she did not mean to be nice to me by not helping me. She meant to be vicious. But she actually helped me...haha, Mom 
Really, it was best that my parents did not give me a place to fall or I would have used it. It was the easy way.
Your son can do better. He just won't. He knows he can overplay it and you'll feel badly for him, but that won't help him. He needs to get out and do what he needs to do to become the man he is. Fretting over it and saying "I can't" does not work when you are of legal age.
Just...please don't quit your job to be his "mommy."
Hugs for all of your hurt and pain. He can do this. You can do this too.
