Hi Liz,
I am so sorry for your brother's illness. I was caregiver for my husband through 3 different cancers. He died earlier this year.
Have you called in hospice? I suggest that it is time to do so. They are excellent with end of life care and control of pain. They know pretty well how to judge when the end is near. There are nurses, aides to help with bathing, chaplains and social workers. They provide all eauipment and meds you need and deliver these to your home. They are kind and compassionate.
I suggest you read the book Final Gifts written by 2 hospice nurses. Many in your position have found it very helpful.
Wishing you strength and courage as you help your brother on his last journey.