I'm not surprised you feel stressed. And I'm not surprised your husband is struggling too. Your mother, much as you love her, is not behaving reasonably. She's driving a wedge between you and your husband, and you can either allow her to do that or you can put a stop to it. In my opinion, the latterstopping heris the kindest and most loving thing you can do for both your husband and your mother.
I think your first priority should be to sit down with your husband and talk to him. Tell him you know your mother is being unreasonable and causing trouble. Talk to him about how whether she's aware of the fact that she's causing trouble or is only doing it because of dementia doesn't matter right now: what's important is that the two of you work out a calm, respectful way to deal with this, and then work together to enforce your plan.
A good plan might be for you both to agree on how much contact you'll have with her. Once you've decided (one afternoon a week, two phone calls, for example) then you tell her you're very busy and want to be able to focus on her when you do get together, so you're going to organise your time to make sure this happens.
She will, of course, object to this. So when she phones you at a time that doesn't fit with your plans, the first time you answer, tell her you're busy but you're looking forward to speaking with her on Wednesday as planned, and then you hang up. After that, you ignore her calls unless they fit in with the plan you agreed with your husband.
If she turns up at your house uninvited, you do not have to let her in. You can open the door to her and tell her you're busy, so can't invite her in, and then end the conversation and shut the door. Expect major kicking-off for a while, but stick to your guns.
When she does visit, if she starts criticising your housekeeping skills or your husband, or anything at all, tell her you're not prepared to discuss that, and change the subject. If she keeps talking about it, tell her you've said you're not going to discuss it but as she can't seem to understand that you're going to leave now, and then do just that. With no further comment. This is more difficult if she's at your house, but you can do it: tell her she has to leave, give her her coat, and show her the door. If she refuses to leave, then you leave. Do not allow an argument to start, do not engage in a discussion about whether you're being fair or not, just keep repeating that you want her to leave now and that you hope your next visit with her will go better.
The aim is to shut down negative behaviours as swiftly and easily as possible. And to put in place a plan which is bearable, and to ensure those visits you do have are as stress-free as they can be.
You and your husband can absolutely do this if you're able to focus and work together. You need to both have firm boundaries in place, to enforce them clearly, and to not allow yourselves to get riled up by her behaviour because ultimately, that costs the two of you, not her.
No, she's not going to like it. But she will learn that her good behaviours will be rewarded and her bad behaviours will result in a lack of contact.