I'm so sorry for what you are going through. Just yesterday, we found out my mom has a cancerous tumor on her liver. Her primary care doctor has been inept to say the least. She has no answers and seems to know nothing about cancer.
We go see the oncologist next week and I am hoping for more answers. My mom does not like to ask questions; she's very passive in these situations, so it is up to me to get to the bottom of what it happening, and you need to do the same thing.
I would highly recommend having your father get copies of his medical records from his doctor and go somewhere else for a 2nd opinion. It's always wise as every doctor has a different approach. And yes, if you have to demand answers, then do so. There is nothing wrong with taking a stand for your fathers life! These doctors in our health care system are just too overloaded with patients and tend to write them off as just another medical record to get results to. Keep on demanding answers and get a 2nd opinion.
I hope this helps! And my very best to you and your family!