My deepest sympathy to you and your family.
How unfair! And out of your control. Two very difficult concepts to get your head around when a death occurs.
Loss of a spouse is an unbelievably hard and stressful thing.
All I can suggest is apply for & take all of the help you can get. Emotional support, financial help, etc.
Are you in a church? Do you have family nearby that you & your son could stay with for a year? O. less bill (rent) might be a life changing savings for you right now.
Don't make any really huge decisions right now, as I truly believe our minds don't function rationally for at least a year after a death.
I know you're not in the position of saving/investing but PLEASE check out Dave Ramsay's book "Financial Peace" (get it free from the library). It has really good tips on saving money and managing what money you DO have. Things like what to pay now, what to let go til next month. For example, do you have a car payment? If so, consider selling the car and buying a used car for cash right now if you can. Downgrade other "options" like cable, telephone service, newspaper delivery, etc.
Do you have an angelfood ministries near you? Good food at LOW prices and no minimum income requirement.
As far as personally and emotionally, please take time to take care of yourself. A grief counselor/group meeting might help you. Try, just try, to take a few minutes each day to breathe and relax. Remember your husband and the 20+ years you shared.
I know it sucks and it's going to suck for a long time. I think time allows us to get used to the suckiness. I don't think grief ever "heals" or "goes away", we just learn to get used to the idea. God bless. I hope things improve for you & your family after this devastating blow.