Hello, Mare. It looks like things are moving quickly for your dad, and that is very good. I had the same radiation and chemo schedule. Although my mouth got very sore, I did not get thrush or candida, so it is not inevitable. The fatigue hits everyone and comes on gradually. He will do a lot more sleeping by the fourth week, and that is normal. It is very good that he will have the PEG, as I did, because sometimes I was just too tired to eat, and my husband could get the food into me while I slept. I have no idea what "tissue breaking away" means and did not experience anything like that. As far as "neck opening up and draining" I think that means burns, which I didn't experience until the last week, but they oozed, as burns do. I think this sounds a lot more terrible than it is. Just take it one day at a time, and it is very doable. Good luck to you both! Let us know how you are doing, and come back with any questions. There are lots of people here who have been there and done that.
Joanna