Father’s safety

Need Guidance on how to deal with my parents. My parents are both 89 years old and living on their own. They bought a house with a master bedroom on the first floor, so they would not have to use the stairs. I recently visited them and discovered that my father has been sleeping upstairs since my mother turns on the TV at 11:00 at night and also will turn on the lights in the middle of the night to read so she can get back to sleep. I set her up with an ipad and headphones and access to books on her ipad, as well so my father will not be impacted by her and he can sleep downstairs. I have offered to move a twin bed into their small office on the first floor – but both are adamant that they do not want a bed in that room. And although she has all the tools she needs not to impact my father – she still is being difficult – she has years of anger at him- and not accommodating and my father continues to walk up and down the stairs twice a day to get uninterrupted sleep (FYI- he hates confrontation). I am worried about my fathers safety….he shuffles when he walks. And I am lost with how to resolve this.