Mom is gone now. I'm left with my S-father who shows MANY signs of Dementia. My s-sister is helping me w/ him. Any help?

If my s-father would need Nsg Home placement (which he definitely needs) my s-sister & I would be left homeless. Our parents had/have a Reverse Mortgage. The Attorney says my s-sister could "buy out the Rev. Mtg.", but I've read so much that says this cannot be done. My s-father is being very difficult & refuses to allow his daughter to buy the house from him, even though it is for his protection. We're trying to keep him in his home. Has anyone else ever run into this type of situation? We want to do the right thing but are both lost when it comes to Estate Law. Is there anything we can do to turn this into a positive solution? His Dementia is very bad. Is it time to let him go and let him be placed into a Nursing Facility? He hasn'twashed, changed clothing ir shaved in over a month! He askes the same questions over and over and has even had hallucinations. He actually scares me. He can be very mean! Any suggestions, similar stories and information would be greatly appreciated.
Thanks... Kathy