I think he is under lots of stress now

You said he went to the best schools and now he is out of job. He is definitely under a lots of stress even though he doesn't tell you.
Be patient with your hu*****and, encourage him and not lecture him. Try your best to help him to get out of rut.
Tell your son that his father loves him. He says nasty things because he is human and makes mistakes. Tell your son he is big enough to forgive his father. Tell him it is not his fault that he gets yield at, and he should feel bad for himself. Tell him everything will be fine.