My stepfather won't let my mother have a life and ruins my day if she tries to get away while I caretake for him.

If you and your mother are planning to continue being your step-father's caregivers at home, you will both have to learn how to stay in control of the situation.
There can be no more "he kept having me call her". The demented elder cannot be allowed to be in charge of a situation anymore. You do not call her. You do not give his delusions or the asinine rambling nonsense that accompanies them any validation whatsoever. You answer him a few times that she went out and will be back soon. Then completely ignore any line of questioning about it. If he keeps repeating over and over again and starts up with the outlandish nonsense about her drinking or being out with an old boyfriend, tell him that you've already told him where she was and do not ask you again. If you have to repeat this a hundred times over, do it but do not call her again for him.
If you're planning on being a caregiver for an elderly person especially one with dementia, you're going to have to learn how to ignore with love when it is safe to do so. You're going to have to learn how to take control of a situation and remain in control of it.
This is often hard to do if the elder is a parent or a parent figure to you. You will sometimes have to be a bit stern with him.

I think one thing you need to know about is "sundowning". This refers to worsening behavior as the day draws to a close. It sounds like this was the case with step-dad today.

Meds can help enormously with the agitation and anxiety that is often present in dementia.

If you know that what you say to him doesn’t matter, or even more important, change his behavior, then why bother to do it?

You are saying that what he says doesn’t “bother” you, but then saying that what he says is “offensive” to you. If so, that’s on you, not on him. It’s a waste of your time to be frustrated and in a bad mood

His behavior is the way people with dementia talk and think and act.

Your job is to learn to accept what he does and says as products of a broken brain, and not related to what you do or how you feel.

When mom can no longer deal with her DHs dementia issues, then he needs to be placed in a Memory Care Assisted Living facility. While he's living at home, you and your mom need to understand what dementia behaviors look and sound like so you can respond appropriately. Yes, these behaviors are extremely annoying but they'll only get worse as the disease progresses. This is why Memory Care ALs are popping up like flowers on every street corner in America. Because family members reach a point where they can't handle it anymore. If you are at that point now, you may want to move out and into your own place. If you're there to help your mom out, then learn all you can about dementia and how to care for your stepdad; watch Teepa Snow videos on YouTube and pick up a copy of The 36 Hour Day as a start. It's a great reference guide to answer your questions as they crop up. Go to Alzheimers.org and read too; they also have an 800 number to call to speak to a trained counselor about the behaviors and get some guidance.

It's good that your mom is able to get out to auctions that she loves and get away from the grind of the endless questions and repetitive behaviors that go along with dementia. It's a frustrating and difficult situation for both of you, I know, so I hope you can figure out a few techniques to deal with Joe a bit better. Definitely do NOT call your mom when he asks you to; the key is to keep him distracted from the constant questions and requests he makes of you, and lead him onto another diversion like a TV show, a snack or sorting nuts & bolts you put out for him on the table.

Wishing you the best of luck!

My father, 89, is starting to do this to my mother, 84. She just wanted to go down to LA for one day to see her sisters, all about as old as she is. A grandson agreed to stay over as the caregiver (he doesn't have declining ADLs or dementia) and all the sudden he's bellowing Nabout how EVERYONE WANTS HIM TO DIE without the Mommy being there personally.

But, see, she enabled this too by saying yes. Yes to all these annoying 1970s behaviors that he once had, like yelling upstairs for Mom to get him supper in his recliner. In the 1980s, she almost left him, but did not. Now she is just resigned to helping.

Hi Bree, Your stepdad has reached the point in his dementia where his short term memory is gone--He's not going to be able to retain new information beyond a few minutes. Because he has no recent memories to make sense of what's currently going on, your mom is his stable reference point and he gets distressed when she's not there. No matter how many times you tell him he won't be able to remember that she's out. He may have started to be lost in time and is accessing memories of the past, even about incidents that were between other people, but the disease causes him to use that memory to 'fill in the blanks' as to what is occurring right now. The main thing to remember is that your stepdad is having more losses than just his memory and this isn't deliberate. Everything he's thinking is real to him.
This really helped me understand what was going on with my mom who has Alzheimer's dementia--it applies to many of the other dementias as well. http://www.dementiacarestrategies.com/12_pt_Understanding_the_Dementia_Experience.pdf
You both might want to check out the Alzheimer's spouse & caregiver forum--like this forum, there are a lot of kind people there who have seen a lot, and have excellent advice and are happy to read a caregiving rant. There's a lot of threads about how to cope with behaviors and caregiving demands, and the choices to make as a caregiver. One option for stepdad might be to find a local adult daycare or have an aide come in to either take your dad out, or do some of the housework so your mom can have a break. Another option might be to think about a dementia focused assisted living or group home, or memory care--lots of resources at the website...
https://www.alzconnected.org/discussion.aspx
Here's a good list of the stages & behaviors seen in Alzheimer's, but they can be common with other dementias too--not sure which one your stepdad has...you may recognize some of these
https://tamcummings.com/stages-of-dementia/
Teepa Snow has excellent videos on the changes that people with dementia experience.
https://www.youtube.com/watch?v=u5QMeQpkPhA
https://www.youtube.com/playlist?list=PL2E2lPBsUeBjA1Utglo8q6yANAijEf8cX
https://www.youtube.com/watch?v=6cZTgG6kDjs
Good luck,

This was my father. Mom waited on him hand and foot. Even drew his bath water. I loved him but told my brothers that if Mom went first I was not caring for Dad.

You can't fix the broken brain. His normalcy is your mom with him 24/7 and waiting on him. When she's out of the house, there's that piece of the brain telling him something isn't right. Allow her more time out of the house and maybe he will get used to that being more normal - worth a try. Redirection of the conversation sometimes works. It's very tiring for those in the conversation with him, but it's part of the disease. Maybe ask the son(s) to come more often to give mom a day out on more regular basis - he seems to enjoy their company.

Your stepfather has dementia. All of this behavior can be explained by this simple phrase. It is the dementia speaking. It makes no sense to someone of sound mind, but every sense to him. I am so glad that your Mom had a bit of time off to do something that she loves. I am certain, living with him, that she is well aware his memory isn't that great. I am certain she understands what you went through, but again so glad you could give her some relief, and the guys with their TV as well. Good on you!
My only suggest is that you get a good read up on dementia, so that you will know that this will be typical behavior for stepdad in future, or that similar incidents are bound to happen. If you find it too taxing, too disturbing, you may not be able to take your place at the helm when your Mom needs just a little time off. But I hope you will. I understand how hard it must be, but given THAT, she has to do it all the time.
The thing about his asking if she had gone out drinking is kind of cute; at least he doesn't think she has another boyfriend (tho that TOO may come!). Best wishes of the new year.
The time may be drawing closer when your Mom can no longer care for him alone at home. And where others cannot care for him in her absence. So time here is limited and is precious. Best of luck going forward.

BreeFitz80: Imho, your stepfather may have been exhibiting signs of sundowning since he has dementia. Speak with his physician about medication(s) that can assist with this.