Geez, I always thought it was "when one door closes, another DOOR opens"-- maybe you're looking for the wrong opening?
I know how awful it feels; we've been in a similar situation when my kids were little (Hubby graduated with a master' degree while his field of interest was in a recession, me working full time, trying to potty train the son and suddenly unexpectedly pg). He even did telemarketing and even worked out of daily temp. agencies just to try to help with the necessities, and finally found his perfect job after 7 months. It wasn't the job he wanted, but it turned out to be the job he's been in for 18 years and has accomidated his MS as his health changed.
Has your husband checked into voc. rehab (not knowing what he does, this may or may not be someplace for him to think about)? What kind of learning disabilities does your son have? Could he go back to the school he graduated from and ask for help with job placement? Seems to me that if they got him through school, it would be to their benefit to help get him in some type of placement in his field.
I do believe that we are very impatient when we try to tell God what to do. He does have his own time and plan, but we do have to help him, also. By doing our part of the work, then placing the worry and concern in His lap, things do turn out for the best. I'll keep your family in my prayers. I have a long prayer list, but there is always room for more.
Take care, and believe!