I have a friend who has a pretty bad job, and doesn't get enough hours to support himself. He has mostly quit job-hunting though, because at least he has a job. He's been stuck like this for quite some time. He did the right thing in taking the job, but then he forgot all about finding a better one!
Basically, if your job doesn't meet your needs and skills, you ought to be spending serious time job-hunting every week. As a corollary, if you are spending 80 hours a week at this pretty bad job, you aren't going to have the time or energy for real job hunting. Overtime at a bad job will just burn you out, and make you unable to get anything better. Cut back to a reasonable schedule any way you can, just to have the energy to find a better job.
I think you should only really quit the job if the only way of keeping the job is working lots of overtime for poor pay, since that means it's interfering with your search for the job you really need.