I suspect my father's wife is being verbally abusive, if not somewhat physically abusive to him also. The nurse at the retirement apartment where they live suggested installing a hidden camera, I had the same advice from my personal counselor. I am his DPOA, his ALZ is moderate stage. In talking with my husband we are in agreement that it probably should be done, but are concerned about how to do it without causing her to become more angry. She contends that she can care for him by herself, but the last two times I have been with him in the past two weeks, his hair wasn't combed (also BAD haircut, hadn't trimmed his eyebrows,ear hair or nose hair) which is highly unusual for him as he has always been immaculately groomed. She also never lets him go anywhere with me alone, always insists on coming along. This is a short term marriage-4 years.
Let us know how it goes.
This is tough, not only for your Dad, but also for his wife, especially since they have been married only 4 years. My gosh, I bet they never thought this would be how retirement would be. Being that the wife doesn't want him out of her sight means she is scared about the future. And also angry that this has happened to him. Plus in denial regarding how much care he needs. You need to put yourself into her shoes.
I wouldn't do a camera. That might cause the wife to pack up and leave, and your Dad would be lost without his wife, as with dementia one depends more on their spouse to give routine to a day.
As for physical abuse, falling can become very common with dementia, thus the bumps and black/blue marks. Aging will also cause one's skin to become thin thus a tiny light bump can make it black and blue. More so if one is taking a blood thinner.
So there is a lot to think about.