Here is a starter for 10 of things that I think are reasonable boundaries:
"I will not sacrifice my physical or mental wellbeing in order to look after my mum."
"I will not tolerate being spoken to rudely."
"I will live with my husband and children." (I really think this needs to be prioritised. It isn't reasonable to expect you to live apart from your husband and your children.)
"I will not miss having quality time with my husband, or my children. My relationships with them are a priority for me."
"I will not miss important milestones with my family (my husband and my children)."
"I will not miss having downtime each day to care for my own needs and nobody else's." (This is SUPER important and so often missed).
"I will not work myself into the ground."
I think one way to enforce your boundaries is to leave your mum's property every time she is rude or disrespectful to you. "I do not accept being treated like that. I'm going home now Mum." AND WALK STRAIGHT OUT AND GO HOME WITHOUT A FURTHER WORD OF DISCUSSION/ARGUMENT/PLACATION. Even if it's half way through a meal. Even if it's in the middle of the night. Stay gone for long enough to inconvenience her. When you return, if she is mean to you, turn around and leave again without saying a word. Repeat every single time.
Regarding not paying for carers, I would approach it the same way I approached lots of boundaries with her. Matter of factly, without emotion, and without asking for her permission. (Yes of course she still has the option of consenting or not - it just doesn't pay with people like her to focus on that). Get as far as you can setting up an account with a care agency. Just do it, book the home visit or whatever. You can say it's just for if you're not there one time in the future. You could arrange a weekend away with husband and children to engineer the "one off" need. If she sulks or tells you how awful a daughter you are... you know what to do, leave the room. Leave the house. "No mum I'm not going to tolerate you abusing me. I can help you to book cover when you're calm and respectful towards me."
There is a phrase, "drop the rope". Don't be complicit in the noose she is holding around your neck. You can choose to stop doing the things that give her something to brace against as she pulls on the rope. Going completely non-contact is one way to completely drop the rope, but there are less extreme ways. Getting a good night's sleep at home with your family is one way of dropping the rope. Tell her that as of X days time you will be sleeping at home. Help her to arrange care cover, but if she refuses, you need to go through with it anyway. You may well have to pick her up in the morning if she has a fall, or change some bedsheets some more times, until she realises that you mean business, and she complies with getting carers in, but do not soften or relent.
Get an alarm pendant or button, and speak to the alarm company about NOT calling you between 9pm and 9am. If she needs help, she will get it from the emergency services. If she is a frequent faller, you may have a department of your local adult social services who come out to help people who aren't injured get up.
I also think it's useful to think of yourself as juggling lots of balls in the air. Some of them are her, some of them are you, some of them are what your children need from you, some of them are your relationship with your husband which does need some nurturing, etc. Some of them, if they drop they shatter and it's an awful thing - you don't want to drop an important medical important for your child, for example. Some of them, if you drop them occasionally, they will bounce. You're already regularly dropping your relationship needs with your husband, and so far it is bouncing but do it too often and it will break. Same with your self care needs. Same with the relationship with your children. These are the balls that you need to focus on keeping in the air. Your mum getting her favourite newspaper every morning by 9am? Drop that ball, it's not important if it breaks. Your mum needs care - but it does not have to be from you. Keep that centered in your mind. You can drop the caring for your mum ball more often. She has a choice - she can get on board with carers, or she can live with sitting in a wet pad or whatever the consequence is, if she has chosen to not replace the balls that you tell her you will be dropping.