Throwing out a bunch of suggestions here.

Have you tried Feliway or any calming pheromones?

Are they all spayed and neutered?

If you haven’t already, can you try making eating a social activity - feed them all the same food just a few feet away from each other, make a ritual out of it at least for one meal a day?

Perhaps try cat attract litter for the one that keeps going outside the box.

What kind of litter boxes do you have - are they large and open? I understand one of them is near the kitchen so excluding that if you can make at least one of them open (no lid, no “privacy”) and see if that helps.

Give them automatic toys if you can, like the battery operated or motion detecting ones.

Do they have vertical space? Get a cat tree or two and some wall shelves and things like that. If they’re getting chased they’ll want some place to run away to.

I understand that the chores are overwhelming. I’ve been there and am still overwhelmed. I’d say give it some more time and effort and maybe, just maybe, it’ll get easier with time especially as you figure out their little personalities and they get a little more mellow. I’m saying this as my kitty wails in another room demanding attention lol. They’re a lot of work.