It's REALLY hard work. I can tell you what I do.
To save myself from another breakdown, I save up what I can for the holidays so we can do some activities. Getting outside, away from the house, new environments - is the ONLY thing that makes it manageable, even to the park in the rain and getting muddy. Double layers & waterproofs. I can't stand the "in the house" activities, craft, baking etc. I spend too much time doing my own chores in here as it is. It's suffocating and it creates more chores.
Ex was meant to share half term with me. He messaged yesterday to say "Oh sorry. Can't" He hasn't seen our two boys in weeks. So obviously I've had them for weeks. It's always up to me to save and plan and I'm getting good at it now.
Yesterday they were up at half 6. Appalling behaviour from the 7 year old, threatening his 3yo brother "Get out or I'm going to hit you really hard" I was disgusted with him - I have not brought him up like that! Because of that I couldn't take them swimming to the "fun splash" (and reward the behaviour). Grandad (luckily not at work that day) took youngest swimming and I made eldest walk/climb 5 miles in the rain to a trig point with our springer spaniel
... backfired though because he loved it!! (so did I, so did the springer) we were all covered in mud but came back smiling and singing!.
Today they'd both been good. We went to a trampoline park, then a free science museum. It was flipping PACKED at the museum. Then a panic amongst staff as a child had gone missing. We left at that point as we didn't want to get in the way of the search. They had wellies on so they played in a fountain pool thing after. Chucking it down still. They got soaked but they loved it. The long bus ride home they sat like angels!! They're now happily playing together with brio. Then really simple homemade quorn & sweetcorn pizza, then the lollipops I've promised them all day if they continue to be good (great for bribing!) and they should go to bed knackered with no trouble. The payoff of getting out is sooo worth it for my mental health!
Tomorrow we're going food shopping (needs must, but they're helping) then bike riding/scooting in the park through the mud and puddles. Waterproofs!
Day after we're going to some glow in the dark 4D golf thing - IF good behaviour.
So my recommendation is to just get out of the house and tire your kid out no matter what. And have a savings pot/account for school holidays!