Paul,
I can relate to being the only one there to take on the troubles of aging parents. As you obviously know, you're NOT alone. Our Lord and saviour is right there with you.
There are times when I think I can not endure one more thing...only to find that with prayer and supplication, I've not begun to scratch the surface.
May the Lord keep you and your father in our Father's Holy Hand... giving you peace that passes all understanding and leading your dad, his team of doctors and yourself and family to the eternal joy of abiding in Him and waiting on His will to be done. If it be God's will, I would ask Him for healing for your dad, and if not, strength and peace for you all.
Shalom, brother. You've touched me heart with your request.