Overwhelmed caregiver

My domestic partner of 18+ yrs was diagnosed 15 mos ago with stage 2 lung cancer which progressed to stage 4. He now has a permanent trach that allows him to breathe and a feeding tube in his stomach for nourishment. These were both necessary since the cancer had moved into the lymph nodes in his neck and paralyzed his vocal chords. He requires almost constant care, and I'm doing this basically by myself. I'm overwhelmed. I recently asked for a family meeting with his three daughters to discuss how I can get some relief and was told that since we are basically a married couple, they are amazed that a spouse would be unwilling to care for him 24/7. It's not that I don't want to care for him, I do...I just need some help. I have no legal responsibility since his daughters all have medical power of attorney. They have suggested that I leave Michigan and go to my place in Florida for awhile but I could never leave him. Can anyone offer some suggestion as to what I can do or say to get some help?