Are there any
other supportive family members that you can turn to for now? A brother, in-law, or even a best friend? You definitly are in need of support no matter where, what, how and the time is now.
You are trying to go at this alone and I tell you from experience that the odds are piled against you.
I would suggest that you separate the problem with you son from the problem with your husband for now. Seek more support from your son's school and solicite help from social support groups.
As for your husband, you might want to seek a second opinion from a different doctor on his depression condition and the medication he is on. I know friends with depression on medications and they all had relapses from time to time.
He is displaying all the symtoms of depression and this is a very diversified sickness where the treatment varies from one person to another and it requires very close monitoring in addition to just medication.
Seek additional professional medical opinion for your husband's condition now, otherwise it might escalate beyond control. Depressed people are unpredictable and very difficult to live with. You must not deal with all this on your own.
My best wishes and prayers to you.