Can I get emergency legal guardianship of my father who was diagnosed with dementia even if he has been married to my mother for 55 years?

My mother (82) is showing signs of dementia as well. She has hearing and short term memory loss. My father is currently in the hospital after he was discharged to her after being in a skill rehab facility. He is 6'2 over 250 pounds and can not walk. He severed two car accidents back to back which may have contributed to him not walking. He was walking after the accidents but progressively deteriorated. He began to fall was hospitalized several times At my dad's request my mother signed him out AMA. He was hospitalized the third time and stayed. My father had gall bladder problems and had a tube inserted to drain the gall bladder fluid. He was referred to a skilled nursing facility/ rehab upon discharge from the hospital. My father was there about a month. My father's insurance would no longer cover his expenses because he refused to walk except when I was there. I live in another state as my parents and would go as often as I could. He would eat more and do his physical therapy when I was there. My father was evaluated by a staff psychiatrist while there and was diagnosed with unspecified dementia with behavioral difficulties. My mother sent back medical equipment ordered by the rehab facility because she didn't like the way it looked in her home. The facility reordered the hoist which she was taught to use prior to him being discharged and the staff taught her how to care for the drainage tube from his gall bladder.. My father was provided with services at home upon his discharge. My father's home is small and thus the hoist would not fit in his bedroom. My mother put a mattress on the floor versus moving his bed in the living room which I was available to help her move. When he got home he refused to sleep on the mattress and slept on the floor. She fed him and changed his diaper. The physical therapist came for a visit and called 911 because my father's breathing was rapid and she was concerned about his overall care, During all this time my father was hospitalized I offered to bring them back to my home to live with me so I can care for them. I have a big home and accommodate them both well. I was willing to take a leave of absence from my job as a social worker to care for them both. My mother refused to sell their home. I go to see my parents and have been actively involved in helping my mom run errands as she doesn't drive and assist her in paying bills. I do not want my father in a nursing home. They have both been great parents and I want to care for them. I am an only child. My older brother died 15 years ago of acute leukemia. My mother is refusing to let me take my father. She believes she can care for my father alone. I can not relocate with them as I have a son who still lives at home. I fear for the safety of my father if he goes home with her. My parents have a few dollars saved but not enough to pay for services at home nor for nursing home services for long term. I spoke to a lawyer who stated to apply for services to cover nursing home care they go back five years and look at the monies saved, My father will thus not qualify for benefits to cover nursing . He would need to pay for services out of pocket which would cost 300 dollars a day, I am in dire need to get custody of my dad. I did research. to get legal custody will take time money and I have go to court to have my mom declared incompetent to care for my father. I am heart broken at the possibility of something possibly happening to my dad because my mom is unable to care for him. My mother is stubborn. So many people would love their children to care for them willingly but not my mom. Please please help me find a way to get custody of my dad.