This all sound familiar. We took care of my Mom in Hospice, same thing with eating. She would get big eyes when I would tell her what we were going to have for supper, but then she wouldn't eat much. I found she liked smoothies from McDonalds, so everytime I went by there I would get one for her. Also mashed potatoes and gravy from KFC. My wife makes a great beef stew, and she would always perk up when she smelled that cooking.
What you are doing is a terribly hard thing to do, I done it with both parents 10 months apart, but looking back on it now, I am glad that we were there to take care of them instead of strangers.
Bless you for what your doing. Caretakers are special, I am 3 time survivor as well and my wife was my caretaker. Couldn't have gotten by without her.