You are in a difficult position....like all of us.
We cannot presume to give you your answer, as others have said you must answer it for yourself.
I liked what someone said above , that you can be his friend even if your partner is in a carehome.
It is my opinion, you must consider your age and how you want to go forward, as staying is a commitment of your time and energy....your life.
I can only tell you that my husband was predicted to live for 10 years when he got his diagnosis, we are well past that -17 years now. He is still physically extremely fit. Life is easier now that he is has even less of his mind than in those early years of the disease. My life is extremely restricted now and I do my best to compensate. I do not always get to do the activities or travel I would like to, but I try to have an active, stimulating life of my own, but I must confess it gets more restrictive with the advancement of his disease.
We were very young when he was diagnosed, he 49 and me 48. I gave up having a sex life, an equal partner and financial contributor to the household, freedom and flexibly. I believe if the shoe had been on the other foot he would certainly have stayed with me and cared for me at home as long as possible.That was a big driver for me.
But as I said the early years were in some ways more difficult...now it clear he is not capable of doing simple things in life, being around lots of other people, communicating and traveling and visiting family. He is not being passive aggressive or obstinate...he is incapable.
Although, I have lost much, I have gained much to in finding new ways to cope, living by principles of personal importance to me, and a continuing lesson in patience and compassion, I am not always very successful.
Our circumstances were quite different from yours as we had more history, and we also have a family together. It was also important to me that my children's opinions on his care were considered. And I have the great blessings of supportive children, supportive friends and some limited governmental assistance and one volunteer who has been faithful and reliable. And TP!
It has worked out for us to stay together, but when I can no longer cope, I will be able to still be loving and supportive if he eventually goes into care.