Give yourself a barrel of grace. You can take a horse to water, but you can't make him drink. Would moving closer to family be an option? Try to do things that make you happy, so he can get a booster by osmosis. I can only offer walks, swimming, art classes which he turns down.
My goal is to keep him clean, safe and fed. If I can accomplish that, I've done something. Anything else is gravy. He was an architect and preferred doing projects rather than interacting with people. He built our young daughters a playhouse that was shown in Sunset magazine. They loved it, but I wonder if the girls might have preferred a game of catch or reading a book together instead. I still get advice about keeping him stimulated and engaged. I can assure friends that put into a group environment, he would be detached and very unhappy to be there. It didn't work before ALZ and it won't work now. ALZ patients are not the same; they bring their lifelong habits and lifestyles with them. Do all you can do, but all you can do is enough. Put "should" in your pocket and just look for tiny wins in a day. I have an active social life online with friends all over the country; at 80, I even have a pen pal I've never met. Not the same as lunching with friends, but I feel in contact with the outside world by chatting about other ideas besides ALZ. It can be all consuming. Keep your head up and keep treading water.