A divorce would not secure your home. It would just include it as part of the matrimonial estate upon which settlement should be sought.Whether you actually end up with it depends on what you negotiate with him. You could secure your right to remain there for the time being (ie until the long term plan of what is to happen to the house is sorted out) by issuing a home rights notice.
If you suspect your husband is suffering from dementia then you should seek medical attention. One has to have mental capacity in order to execute a new will so if they do not have the requisite mental capacity then any Will executed would be invalid.
In the event that he dies having made a Will leaving it to others then documentary evidence of your concerns of his mental state would help.
If you husband has capacity, is going to leave his estate to others, and you do not think you could make a claim on his estate because you are not dependent then the only way in which you may end up claiming some of his share of the matrimonial assets (if he has more than you) would be to divorce. But again, if he is in the early stages of suffering dementia and is likely to require a greater income/assets than you for his care then this will be a relevant consideration and perhaps result in awarding him a greater share.
I can't tell you to divorce or not. In order to divorce though the marriage must have irretrievably broken down. Whether it has is for you to decide.
I really think you have to seek some specific advice on this from a local divorce/contentious probate solicitor, they can advise you specifically after you have provided them with specific information of your assets/his mental health etc.
It does sound like a very difficult situation, you have my sympathies.
Edited by Thomas on 10/26/2010 at 10:43 AM EST