Your dad is in my prayers! All of ours, it seems!
This might sound weird, but I chew ice a lot under stress. Its the motions of chewing and holding a cup of at least something that comforts me. And Ice usually does it. When my grandmother was in the hospital I had a large soda cup full of it that I would just chew through.
I don't know what makes you eat when you're stressed, but maybe just going through the motions would help. I hope everything goes well, I know a million people a day must be telling you that, though. So just know you're in my prayers.