No need to apologize.... really! I know what it is like to feel so overwhelmd and depressed. It is not easy..... and sometimes you just have to put one foot in front of the other.
My Dad was really horrible while he was sick. He was very angry, and took a lot of that anger out on those around him. I've been there. And there are times you just have to leave. It doesn't mean you love him any less, just that you can't deal with his behavior. My Dad pushed both my sister and I away, and took a lot out on Mom.... I honestly don't know how she was able to deal with him for so long. I am the oldest child, the son, and I eventually had to have sort of an "intervention" with Dad and the whole family to let him know how his bevior was affecting everyone around him, but also to tell him that we were all committed to supporting and helping him whether he liked it or not. It was extremely emotional.... it had gotten to the point where he was more like a child we were looking after than a grown man. But it worked to some extent, he wasn't quite such a bastard afterwards. I don't know if anything lie that is possible in your situation, but know that I have been there.
As difficult as it may sound, please know that it is very important that you make sure that your own needs are being met... as far as eating, sleeping, support or counselling. I have said it before.... our loved one may be ill, but we are ALL battling cancer. Sometimes I wonder if one of the resons my Dad was so horrible when he was sick was some misguided attempt to have us all feel relief and not grief when he died. Who knows. It is sure not easy.
Nite