How do you deal with empathizing for a declining parent who also sucked?

Thanks for anyone who reads this way too long rant — I did some bolding to make it easier to skim lol, I felt self-conscious about how long it is. It was helpful to type out I guess. Trigger warning: brief mention of suicide.

The TL;DR is that I had a really bad conversation with my declining father (83) who has always been a difficult person. We talked about moving to assisted living to help my mom (68) who takes care of him. He said a lot of really sad things about his life and how he's feeling, but also a lot of mean and vindictive things. I don't know how to think about it, or how much he knows what he's saying, or what how to process any of it emotionally or philosophically or how to think about what's fair going forward.

My (83y/o) dad has had dementia for a few years. Currently, my mom (who is 15 years younger) lives with and takes care of him. He's lost lots of daily function, tons vocabulary, can't tie his shoes or use a computer and obviously can't manage his own dr's appts or get himself to them. He's fallen seven times that my mom knows of in the last month but she thinks he's hidden others, and had two unrelated days-long hospital stints.

Importantly, they have a terrible marriage. He has always been a selfish, domineering, judgmental asshat. (I went low contact with him for years before the decline, but he's gotten sweeter and less combative as he's lost himself.) I don't think he's admitted fault or apologized for a single thing in his life, the sort of guy who would knock a glass off the counter and say "Who put that in such a stupid place?!" and get mad. You know the type. My mom agrees. His history is not really helping the situation.

The biggest issue is that he has totally lost the ability to occupy himself. He can't retain things well enough to read a book, can't use his phone/computer, can't understand the plot to TV shows so refuses to watch without someone explaining it to him along the way. My mom organizes and takes him on activities each day, talks him through movies, works to stimulate his brain. She spends hours going through his emails with him so he can stay in touch with friends. This alongside everyday care stuff. She's losing her mind, and is hiring in-home help for a few hours a few times a week but the issue isn't really cooking or dressing him, it's the emotional/mental weight of his needs.

She does take breaks — he's in an adult day program 2x a week, he can be home alone for a few hours — but it's a lot. My mom just retired ~18 months ago planning to do volunteer work, tennis daily, travel, etc. which is obviously hard bc of him. She also was just diagnosed with Parkinson's and macular degeneration. She is overwhelmed with managing his care and struggling with the idea that her life might be over at 68.

So I tried to talk to him about being open to moving to an assisted living facility. I didn't expect this to go well, but my mom said she'd gotten him to agree a few times that he would have to move separately, even if he forgot later. And he used to want to move to assisted living to have activities and new friends, even picked out a place he was excited to go to when it was time. I figured my goal was a lesser one, which was pointing out that it was now time. So I didn't expect it to go as badly as it did.

Despite how he treats her, my dad is, and always has been, obsessed with my mom, so now he is refusing to move because they'd be apart and all he wants to do is be next to my mom. In response to the suggestion that my mom is overwhelmed, he got really angry and insisted that my mom barely does anything for him, told me she only spends "15% of her day or less" with him and that she has "a chip on her shoulder." He was saying that he's totally fine and doesn't need help, that she's the one who needs help, and at the same time said that she's not doing enough for him, that he can't do anything without her and yet she does whatever she wants all day etc.

He then went into a really sad but also still awful rant about he wants to fix his marriage and how my mom doesn't like him. But the only thing he wants to do to fix it is make sure she is with him at all times. He's actually excited that she has parkinson's because he thinks she will decline and be on the same level as him, which I think says a lot about who he is as a person. (She's also still OK and is responding really well to meds so I think she has at least several years of living life unaided.) He then ended by saying that if my mom and I wouldn't "be nice to him" he would shoot himself.

That was pretty traumatizing as an ending and freaked me out. But I'm also pissed. I know that he has dementia and he's not really capable of understanding what she's been doing for him. But it was so in keeping with how he has always been, in the worst ways, it was triggering. I don't know how much he can even really understand any of this or be responsible for his words. But also in this conversation he spoke more clearly than he has for years, didn't miss words or stumble, and seemed totally lucid. So I'm just really confused about how to feel.

Like, I do feel really bad for him. Maybe asking him to move is unfair, maybe I'm only thinking about my mom. I'm worried I'm not having enough empathy for him. Of course it is terrifying and awful to lose yourself like this, to know (at some level) that you're a burden on everyone around you, and to (at some level) realize that you don't have the love and relationships you wanted in your life at a point when it's too late to fix it. It's awful. He said all he wants to do is be nice to people and have them be nice back — I can see that inner child. What he's saying is he wants his wife to want to spend all her time taking care of him, and love him, and he is deeply hurt that she doesn't. It's heartbreaking!

But also he made that bed, and I'm not sure how much more kindness anyone owes him; he's already gotten a lot and I'm not sure he's capable of being kind. And I guess the flip side is that this conversation was evidence that he is still in there and the him that's there is the same old asshole. I'm furious at how he's speaking about my mom, downplaying what she's doing for him, his usual denial of the legitimacy of anyone else's experience, his insistence that she's the problem because it can't possibly be him.

Sure, it's sweet and sad that he wants to fix his marriage, but his vision of that is him getting to spend more time with his wife the way he wants, while adamantly denying the legitimacy of her needs and experience. That's the same reason the marriage needs fixing in the first place. I think his version of love has always been having someone just be a mirror image of him, his values, his preferred activities, his taste, and any deviation from what he wants he understands as a deep betrayal. It was like this with me, too.

I know that he has dementia and maybe he can't understand. I know there's no point in feeling mad about it. But it's also so in keeping with how he has always been. It's the same shit as always; nothing could possibly be his fault. He said the only thing he wants

And, of course, the dementia isn't his fault! But also he's doing the same thing as ever. There were moments he appeared to recognize acknowledge his impact on my mom, like he said at one point that he stays up at night worrying that my mom can't travel or live her life because of him, but then he seemingly shoved that thought down and went back to saying that any overwhelm she might be feeling was irrational. Same shit as ever.

Basically I'm just stuck going in circles. I remember how he was also a good, involved dad when I was a little kid. (Before I was old enough to disagree with and thus "disrespect" him.) I remember him driving me to hobbies and making Christmas magical for me, and can see how much he cared and tried. I think about how he was probably doing the best with the emotional resources he had, how he probably did better than his parents. But every time I get sad and feel guilty, I remember how demeaning and controlling he was the second I wasn't in elementary school.

Arguably my mom signed up for this to an extent when she, as an adult in her 30s, married a man on the cusp of 50, and then stayed with him for 35 years. Maybe my mom is being just as selfish as he is by not wanting to continue to care for him throughout his decline. But I do think she's tried her best. Maybe her best isn't good enough, I really don't know how to think about it. She feels incredibly guilty — she told me crying the other day that she wishes she did want to spend all day just sitting with him like he wants, but she just doesn't. It's hard.

I guess what I ultimately think is that the fact is that she's increasingly broken, whether or not she "should" be. And maybe there's no perfect solution, but there is a solution that could help. And that is for him to move into a facility! Not everyone has this solution. We're lucky they can afford it. Maybe he'll hate it. (Though honestly I think he'll quite like it; I don't really think living with a wife who cares for him but also resents him is good for my dad either.) Ultimately I guess I just think answer should not be to ruin one person's remaining years just to improve another's.

Anyway, don't know what I'm posting this unbelievably long diatribe for but if you made it this far, thanks.