When is it time for my husband to go to a nursing home?

If he is content, and physically as healthy as anyone be expected to be at this point in his life, then I think the decision to place him rests on your own physical and mental health and your ability to continue to care for him. If you can bring in aides to help with bathing and to take over other household chores would you be content to keep him at home?

Getting help to come and assist with some of his care sounds good, but, the problem is that if he resist being cleaned every time, then there is no way that you can just wait until they arrive to clean him, since his BM's could come at any time and at multiple times during the day. It's a tough situation.

I'd consider how feasible it would be to have outside help come and stay all except overnight. That way they could do all of his bodily care. Maybe, he would adjust and not resist them. Sometimes, people with dementia do better accepting personal care like that from professionals. They are trained to handle that kind of thing. Still, a lot will still be up to you. It's a huge responsibility. Plus, the costs for that kind of care in the home is huge. If funds are not available, then, I'd consider what other options you have, such as the NH. It wouldn't hurt to consult with some experts and get all the options. Don't forget that you have to take care of yourself too.
How long since you had a break from caregiving?

Just on the one point, where you say if your husband won't cooperate with you you can't imagine he will for a stranger: you'd be surprised. Your husband feels comfortable arguing with you. Faced with a whole team of competent professionals, it would be a different story. They have ways of getting the job done that brook no resistance - and not in a mean way, so it's not as horrible as that sounds.

Why not give it a try, by seeing if you can get him to a nursing home for a week's respite care? If all goes well perhaps the stay could be extended; and even if he doesn't settle and you decide to continue care at home, at least you'll have had a proper rest.

According to a study published by the National Institutes of Health: "The main predictor of life expectancy is the age. Therefore caregivers, patients, and their families could plan on a median life span as long as 7 to 10 years for patients whose conditions are diagnosed when they are in their 60s and early 70s, to only about 3 years or less for patients whose conditions are diagnosed when they are in their 90s." (Source: Life expectancy in Alzheimer's disease, Zanetti et al. Alzheimer-Memory Clinic, Brescia, Italy)

Your husband is 90. Perhaps it's time to think beyond nursing home and inquire about hospice. Does he have a living will? A DNR? Not wanting to eat is an indication that his disease is progressing. I encourage you to talk to hospice about the pros and cons of artificial hydration and nutrition.

I think you may be jumping the gun in suggesting hospice NYDIL, not being hungry is not the same as refusing or being able to eat, my mom has had zero appetite for years. She is also incontinent, can not stand or walk, and doesn't know her own name, but she is otherwise stable and unless she is carried away by a stroke or heart attack we all believe she could carry on this way for years.

I don't see how putting a 90 year old man with Alzheimer's in a nursing home is going to do him any good. It's just one perspective that people have when quality of life is weighed against quantity of life.