I might sound crazy but I think this is a golden opportunity to you. It doesn't matter whether he took an overdose or it happened by accident. His condition has probably put you over the top in your nurturing and caretaking roll. Of course you are worried about him and feel very sad. I think you are getting more in touch with your feelings that you can no longer take the caretaker role. It might be a new beginning for you. Sadness is appropriate.
Guilt isn't. Anger right now is probably appropriate because you are fighting your nature. He is not your problem. Your ability to hold down a job makes you a hero. Your marriage sounds demanding although from what you have written in the past, your husband sounds like a wonderful person. I wasn't aware that he had problems too so that means extra emotional stress on you.
Maybe this incident will help you to start to weigh things and only do what you are capable of doing and begin to give up the caretaker role which is so much apart of you. It will be a big battle but it is amazing but the guilt diminishes.
Bobby