I agree with mickyc, if you can afford a week off or even half a week than do that and take some time to re-energize yourself. It is like any other job and holidays should be taken so that we can avoid burn out.
Sounds like some of the behaviour is age related but could it also be boredom? I know it's time to do a toy change up when the kids start to get restless,argue and just aren't playing nicely. I do a half toy rotation about every 2 weeks and a book rotation weekly.
When I'm feeling in a rut, I check pinterest for some new fun ideas and art activities. Maybe try that?
Keep telling yourself "this too shall pass!".....it sorta helps lol