sounds like that needs professional intervention by a therapist, social worker, etc.
And, you know, for both of you.
You may need to do more professional and detailed research about his condition.
For example, you may be ascribing emotional indifference to something which is, in fact, not emotional, but a physical medical problem manifesting in that way.
you can probably find support groups with other people who are dealing with these issues, and get some support from them.
Separating from a spouse with declining cognitive function could be extremely destructive. If separation has to take place, a long period of work should be done prior, so that your spouse has an entire support system available to him, before you depart.