His behavior, as you know, is the dementia. At this point, with him in a steep decline and you on the verge of burnout, the kindest thing you could do for him is to let his case manager/social worker know that you can no longer devote your life to caring for him and he needs to be in a facility. Then let them take the measures to put him in the facility. His anger hopefully will be directed toward the social worker and once he is settled wherever he is going to be, you can become FRIEND again. And at that point, that's exactly what he will need, a friend.

He will probably perk up with the social stimulation and the staff will know how to redirect and minimize the bad behavior.