I'm so sorry to hear about your dad's vomiting. My mother in law also has PC and is in the last stages. She lives with us and I am her caregiver. We received the diagnosis in October of 2006. I understand what you and your family are going through.
Has the doctor mentioned hospice care yet? It sounds like it might be a good time to look into it. (www.hospicenet.org is a good place to start.) Since you know things are in the final stages, having extra help for pain & the caregiver(s) can help make things smoother for the family.
Have you asked the doctor if the feeding tube is still the best thing for your dad? There may be a point where the feeding tube isn't helping because of the damage that the cancer is doing to your dad.
Best wishes to you & your family!