I am so sorry. I do not know what to really say to you. You are being so brave. I can tell that you and your father are very close. He sounds like an amazing man.
I too had a similar situation except it was my mother who was 53. Mind you I am 32. The only thing that we found worked best for us was to just live for the moment. At this point the little things are everything. Just sitting with him and holding his hand while he sleeps is probably a comfort to him.
I am not sure I have anything medical to offer you but, try your best to talk with the doctors and nurses. They may even be able to recommend a counselor to help you through this.
You are not alone my friend.