This may be as good as it gets. When you said you told him about the job fair, and his reply was it's part-time and not 'his' position, I asked myself where in the hell is his pride? Why isn't he helping financially? He should be pitching in too, even if it's flipping burgers.
When I got out of rehab, I took a full-time job as a nurses' aide at minimum wage because I had an 8 year old daughter to take care of.
He's got no inclination to do anything different because what you are doing is working for him. You're the sole provider.
Is this what you are willing to settle for? If not, you need to start making some changes.