The fact that you are aware and understanding of his dementia places you ahead on the learning scale. As you know therapy does not work with Alzheimer's, there is one medication that has minimally effective results is slowing progression and improving functioning (again minor not miraculous improvements, Unfortunately, there is not much more than you can do and the deterioration will be slow. But it is one of those situations where you are essentially helpless except for your understanding.
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If there is something specific that I can respond to please ask-sorry I missed the heart of your question. But that is the ood thing aboput JA-to be able to rectifying short comings