Sue,
I am a caregiver as well and we are often emotionally drained. I am currently in counseling to get the support that I need. She said something today that rings very true. If my husband gets cranky or upset he sometimes snaps a bit. My counselor said that I should remember: sometimes destructive behavior is rooted in fear. If your husband takes things out on you perhaps it is his fear coming out in ways that are not fair but might mean that he is really afraid. I asked my counselor how I should react if my husband says something that feels hurtful. Again she came up with good advice: if he says something that is inappropriate or hurtful then you need to calmly say that what he just said hurt me and so I need some space.
Try not to engage in some of the fighting and walk away. As Christine said, you know that you are doing everything that you can. When this has all passed then you can make whatever decisions you need to. In the meantime, try to untangle and disengage when he gets rough, you DO NOT DESERVE IT!!!!!!!