I am so sorry to hear about your Dad and all that you are going through as a family. I have no knowledge of his particular cancer type but think that a second opinion is a must so that you can all make informed decisions about treatment. It is amazing what is available when you research - nanoknife, cyberknife etc are now proving very effective with certain tumours and the consultants are normally really helpful and will email you with their thoughts at no cost. You are entitled to a second opinion via the NHS but must also be prepared that a lot of these treatments are only available privately and the NHS doctors are not always very knowledgeable about them.
I am lucky to have medical insurance and would definitely have had a much shorter prognosis without some of the treatments I have had. Good luck to you all x