Is my stepfather's anger normal?

Since he said "read a book about it" maybe that is what you need to do. There is a you tube show TippaSnow? (Someone will correct me) that explains what happens to a person suffering from a Dementia and how to deal with it. At you tube put is "search" "Alzheimers videos". A list will come up, pick the one with the yellow brain. Takes you thru the stages.

Other than visit, do you help at all. Like asked, do you bring a meal. Do you clean. Do you give SD a break. Stay long enough for him to get out for a while. Take Mom for a ride. Caring for someone 24/7 takes a lot out of someone. You are dealing with, basically, a toddler. Mom probably has no short term memory. Doesn't have the ability to reason or have empathy. Can't appreciate what her DH does for her. She probably asks the same questions over and over. Thats why he is tired of answering yours.

There will come time when SD cannot do it anymore and may need to place Mom in an AL or even LTC. Be supportive. Unless you have cared for someone with a Dementia, you have no idea. Maybe you should give SD a vacation. Some respite. You care for Mom for a week and then you will see how she is.

I don't know how you are asking the questions. He may be feeling that he is "being questioned" if you know what I mean. That he is taking care of her, and you are there instead of with support, with questions. You can imagine his life now is nothing BUT questions, from his wife, your Mom. And from medical personnel. I suspect he is very frustrated.
What questions exactly do you have for him. Could you give us a few for instances? You understand that your Mom has Alzheimer's. HAVE you read a bit on it?
How about just visiting and saying "Dad, how about you go watch a game and relax; take a ride and relax; go to the workshop and relax". Take a casserole with you so Dad doesn't have to worry about meals. Ask how you can help and what you can bring. Tell him that you want to support him in his excellent care of your Mom and tell him to let you know what ways you can help.
I suspect your Dad is depressed, and anger often is a manifestation of depression. I can't know what you are saying or how he is responding. Or if you ever had a strong relationship the two of you. But these are just some things to try, and I wish you the very best of luck.

Oooh, now.

This SO much depends on what questions you're asking.

Have you done the wider reading as he suggested?

It's only a guess, but judging just by what you've said in your post I would say that his anger would be completely normal for someone as stressed as he sounds being asked what he might consider to be dam'-fool questions.

I agree with most of the other comments here and can speak from my experience. My husband’s daughter comes around to visit and asks questions as if she is second guessing my (and his doctors) decisions for my husband plus she can be very condescending. I have mailed her the 36 Hour Day book but I can tell she hasn’t read it. She has no clue plus I think she’s in denial to a certain extent and doesn’t want to accept her father is not the same person anymore. My saving grace was that she lived out of town and wasn’t around all the time. Now she is moving here so I may have to nip things in the bud if she becomes overbearing. I have been generous with information but I cannot allow her to “upset the apple cart” if her visits/questions become too much. I don’t know what questions you are asking your SD but please come from a place of concern and not judgement and after you have done some reading up on things. Offering him respite is a good idea.

It is not easy being the caregiver, especially when your charge has dementia. Take his advice and read up about Alzheimer's disease. Then, contact him - when you are not visiting mom. Let him know your concerns are not about him doing a "bad job" but about how you can be an asset, a help, to both of them. Keep in contact with him when you are not "visiting" so that your in-person visits can focus on connecting with your mom.

Im sure we haven't heard both sides of the story.

Do you adk a question or have you been drilling him and your questions feel more like accusations like maybe he isn't doing enough for your mom?

I'm sure he is coping the best way he knows how. It isn't easy.

Actually reading up on alzheimers is actually a very good idea.

The Book will be able to give you a lot more answers then he would anyway.

You would need to put yourself in his shoes, it's very sad having to go thru living with a loved one with alzheimers.
I'm sure he's got a lot of questions himself and wonders what's going to happen next and when the time will come that she won't be able to live at home any longer.

You should let him know that you want him to know how awful this must be for him.
You should offer to to spend the night or a whole weekend once a month to give him a much needed break.

Let him know that you understand him not bring there when you visit, he needs to be away and get a break at least once a week.

Be pleasant and bring gifts when you visit.

Bring or buy flowers, a meal or dessert.

Clean up the place a little while you're there visiting your mom.

No one understands until they do it, that being a 24 7 Caregiver is horrible.

Prayers

He is probably depressed himself. Moreover he will not feel like running everything by you - it depends what your relationship was like before.
My stepfather was not very forthcoming about my mother at times and it takes a while for everyone to readjust to the changes. As our parents age we ask more questions out of concern but maybe it feels like intrusion. Over time it becomes the new norm.

Maybe not anger, probably frustration and burnout. He is her primary caregiver and tired. It is very difficult to care for AD 24/7, some do not want to talk about it. It is quite the emotional rollercoaster.

Have you offered to help? Maybe accompany mom to the doc? Have you sought out caregiver support groups? Try reading the 36 Hour Day.

What can you do to support dad? Are you critical of how he cares for mom?

If he is mom's POA it is actually his job to keep mom's information private. Maybe is honoring mom-s wishes to not want to bother you with health issues?

Teepa Snow

It sounds to me like he is burned out big time. Next time, if mom appears to be ok, talk to him to ASK what you can do for him. Does he have kids of his own? Offer to stay w/mom to give him a couple of weeks off and out of the house. For a period of time, don't make conversation about mom. Make it about him. The visit w/mom separately. You might ask if he'd like you to clean house for him, do laundry on regular basis, or even pay someone to go do chores for him. It might take a few visits to turn it around, but worth a try