Hi Lisa,
I am totally new to this as well. In fact I just registered as a member about an hour ago. But all the feelings you describe are so familiar. My mother died in my arms from lung cancer in March of 2001. We were in her cherished home.
There was only 2 or 3 months where she needed to be checked on frequently and meds throughout the night, but I still don't sleep through the night. Everything went just the way she had wanted it to, including the DNR order, and I think that's the greatest gift I could have given her; to be with the two things she loved most while passing - me and her home.
This is such a tough time for you. The best advice I could give is to go ahead and experience your feelings. Be careful how you express them them, but do experience them. And spend time, when you don't have to be the caregiver, to just sit and hold hands. It helps to acknowledge the reality of the situation without getting caught up in the sadness. Good luck. You'll both be in my thoughts and prayers.