First off Nell, you really have to try and control and distance yourself from it.
He will be like a stranger to you, they all are even mine, yes it is uncomfortable talking to them and yes he will be lovely one minute and horrible the next. He may very well be getting coached or it just the aliens in his head. You will never predict his behaviour and you won't understand it,that is why you have to stop yourself from getting emotional over it and forgeting the rules of DBing.
You have to start looking after yourself sweetie, I know the first time H left me in June, I couldn't move off the couch to go to work, I didn't go for a whole week. I didn't eat, I didn't sleep, I drank too much wine and ate way too much chocolate, then I realised that I was only hurting myself not my H. I now make sure I have a healthy breakfast and lunch (yes you will have to force feed yourself to begin with, but DO IT), I eat dinner depending on the time I get home from gym so dinner is up and down.
You have some time, so go and redo your hair, put on a nice outfit, put your makeup on, perfume and have a meal ready even if it is only for yourself, make sure he sees you are pulled together and the house smells good from cooking. Don't let him think for one second that he is getting to you.