Focus on your fathers personal and emotional needs and talk about everything you need to say about today the past and the future. It is a fast disease and your time goes quicker than you think so don't put anything off. The doctors have no idea of how long you have as I was told 18 months and we had just 3 weeks. Get a lot of support from friends and family and have them do the research to find out what additional options to traditional medicine you may have with diet, supplements, Reiki and prayer. While weight loss is a concern I would avoid sugar as it feeds the Cancer and focus on adding cruciferiouss vegetables in supplements or eating if possible. This is what I was told by the doctors and nutritionists. Find out what is a good hospital to go to if you need to so you do not have poor care to add to this struggle. The doctors unfortunately are not all helpful as they are many times emotionally disconnected. I went to the Mayo Clinic and they were great and were primarily focussed on my mom's health and pain in comparison to our local hospital and doctors who would not drain her stomach or assist in the swelling of her feet. You are your Fathers primary advocate so don't wait for others to help.
My Prayers are with you as I also know of many who have fought this a long time.
Troy