Hi there --
Welcome to Just Answer .
Has any blood work been done on your dog since all of this began -- to rule out any underlying issues?
The biggest question that I would have if this were my patient -- is whether there is an underlying cause for the behavior you are seeing --
Dementia itself is not a life limiting factor -- but the cause behind it can be.
and some of these symptoms are siginificant.
Heart failure of liver function could both be a factor behind such symptoms --
There are medications specifically for dementia in dogs ---
and the supplementation of melatonin is also sometimes used -- but please consult your vet regarding this -- as you do not wish to do harm if there is an underlying condition.