Oh Merlotgran, I am so, so sorry. I have just read your OP.
What devastating news and it's no wonder you feel as you do. What agony, for you and your family, and also for your dear daughter.
I know many of us know the utter pain of wearing a mask, trying to be supportive, positive, helpful but all the time just wanting to cry, and feeling so helpless and hurt. A terminal diagnosis means life stands still and what used to matter, doesn't matter any more.
My thoughts are with you Merlot and I do help sharing your feelings helps you to unload a little in a desperately sad situation.