Seana, you really are doing a good job and you've been taking care of so many things, it's certainly understandable that you could get stressed. You emotions are as important as your health and can affect each other so you do need to try and relax.
As Maria notes, the Buddhist meditations and breathing are a great help. My son and I both did them while he was surviving and we still do them even now. You could start with taking 10 slow deep breaths, while thinking only of how the breaths are going in and going out. You might find that other worrisome thoughts come into your head and when this happens, just tell them to cut the "chatter" - then start over with the deep breaths. (Sometimes when I can't sleep I have to start over several times!) As a caregiver, you are a very important part of your husband's getting through everything he has to deal with. You need to take care of yourself so that you can have the physical and emotional strength for the tough caregiving job you are doing for your husband.
I think that CherylD has good advice for you when she says:
<<Ultimately you've done all you can - I do understand it may be the drugs or him trying to deal with the after effects, and reality, but what he's doing is still not right. Do not abandon him, but you have children to worry about.. Tell him as much, tell him you're there for him, then back off and focus on you. >>
A long time ago, when my son was being "difficult" during his recovery, a very wise lady on this forum told me to put my "nurse from Hell hat" on and tell him what he needed to do. So I did and it worked just fine. I think the change my son saw in me that day is what did the trick. I hereby pass on my "nurse from Hell hat" to you in case you want to use it.