It simplifies matters if your husband is the only child - yes, you get no help from siblings, but on the other hand, they aren’t usually much help anyway - especially if you live with your MIL…and it certainly makes it simpler about the money. What you do NOT want is for YOU to do the caring, and then siblings swan off with lucrative chunks of her estate when she dies!!!
I think you and your husband do need to sit down and work out the finances - how much is the house worth (get it valued for free by an estate agent) and then you can see whether, If you ‘crack’ and just can’t stand looking after her any longer, and she has to go into residential care, just how much of the house value you are likely to lose.
The trouble with dementia is that it just ‘gets worse’. My poor MIL eventually ended up doubly incontinent, couldn’t talk, and couldn’t move (bedbound or in a wheelchair). Dementia will ‘kill’ in the end, but to be brutal, it is ‘kinder’ if something like a stroke or a heart attack gets them first…
How close to 60 are you and your husband? If you can ‘tough it out’ till you turn 60 then you may have the house protected against being sold. As others are saying, that your disabled daughter lives there may also help your case.
Why do you think your husband is burying his head in the sand over this? Does it hurt him emotionally too much? Understandable, but he MUST face up to it… Can you leave him to look after her for one entire day ON HIS OWN (eg, at the weekend) so he knows just what you are coping with, and just how WEARING it is. You never get a moment’s peace…
That said, as the dementia worsens, she will likely get ‘easier’ as she will sleep a great deal…my MIL nodded off all the time, as it progressed. It’s all sad and dreadful, but there it is.