He is absolutely heartbroken that I am married to my husband and not him. He keeps asking how to make things right between us, and crying about it. I have tried to redirect him, deflect his comments, explain how I’m his daughter, and his wife has died. He was married to my Mom for 25 years then divorced, and was married to his 2nd wife for 35 yrs. I think the fact that I have had to do personal grooming/bathing for him lately started this delusion (dad is very modest). I am looking for any help I can get regarding this!
This is extremely common in later stage of dementia.
I think that the best thing you can do is educate yourself by online research on the disease and by watching a whole ton of Teepa Snow videos about communicating with elders with dementia (youtube, still, I do believe). Also consider getting some books on the subject.
There will come a time when it is really not sustainable to attempt to do in home care. When visits are better for yourself AND for the person suffering this disease. I think you may be coming to that conclusion yourself, and only you can make the decision in that regard. Other than that there is the simple and repetitive "No Dad, I am not _____; I am _________". Won't work for any amount of time, but there you are.
I am so sorry.