Good grief. You have a lot going on. Best wishes to you, regardless of what you decide. If it gives you peace of mind that you have tried everything, absolutely without hesitation ask for a second opinion outside of the group. It's your life, and you're in charge. Most likely, unless there was some major mistake in the reports along the way, they will say the same thing in my opinion. Otherwise, they have quite a collection of jerks for doctors there.
I am a caregiver for my dad who is also diagnosed with an advanced cancer and six-month prognosis. It's a balance scale, with the desire to live on one side, and the desire for quality of life in whatever time is left on the other side. Do we want 4 relatively good months, or 8 horrible months, and how do we know we made the right decision. It is a tough place to be, and we feel what you're going through. Good luck to you, and we're still hoping for a miracle for everyone.