I can totally empathize with your situation
I don’t have difficult kids but definitely can relate to some of the other stuff.
Please get the book “finding your smile again” and read the sticky on this page about burnout. Some great resources. I think it is easy to say give up but if this is your only way to earn money I would do that as a last resort. Boundaries are key and from your post I can see that you feel exhausted, under appreciated and without any joy because of a lack of boundaries and tolerating way to much crap that you do not want to take. You have to know yourself and what you can handle and then stand up and create some boundaries around your mental health. My kids had their own toys and daycare kids were not allowed to play with them unless my kids said so. They also had different rules from the daycare kids and that helped a lot. They felt special. I went to an educator conference and the people there said this was a healthy thing to do.
Right now for me it is boredom so I am trying to make a plan to get rid of boredom as best I can. I also hired a cleaner to do some of my cleaning so that on the weekends I can get out of the house and have fun! I want my entire weekend to be devoted to getting out and having fun. No more cleaning on the weekend. Every little bit helps