Hello. You don't know me, but in 1983 I was in your situation, seven months pregnant with my son Eric who was found by ultrasound to have "multiple abnormalities". I had polyhydramnios also, the amniotic fluid was not going through his digestive system. Your journal entry filled my mind with memories and my eyes with tears. I will pray very seriously for the three intentions that you ask. When Eric was in the womb, he had five older siblings at home. We faced similar dilemmas.
I don't want to go on about my own situation, but just to reassure you. We placed ourselves in God's hands, as you are doing. We prayed and asked for prayer. We turned things over in our mind we followed our instincts and our Catholic teachings. In the end, we experienced the love of God, the joy of Eric's short life (100 days), and the connectedness of all of our children with their brother to the extent that they could understand his situation. Our trust in the Lord was never, ever put to shame. He guided us with compassionate grace and brought us through every twist and turn of Eric's life and health. He will do the same for you. I do not presume to be able to know or guess what your coming weeks will bring. But please believe that I have your backs, prayer-wise. And I know that the goodness and mercy of God are far beyond the power of our hesitations and our fears. You are right to love Frank and to support him in the life that he has. Because he, like you and me, like all of us, has a life and is living it. None of us know how long we will live. Frank is living his life in the heart of a family that loves him. His life already has a richness that no physical outcome will negate. May you be blessed with every tender mercy of our triune God.