@Pallaska You're clearly a nicer person than most! My DW would lose her shit if someone reorganised her kitchen cupboards without asking. I mean, those cupboards are exactly the way she wants them & they're the engine-room of her care for our family. She knows where everything is & everyone else has learned not to mess up her system. How dare anyone muck about with them, thinking they could do better?!
My MIL is capable of being fairly manipulative, too. One of her favourite tricks is to moan on about someone's behaviour towards her - eg her son, or her boyfriend, or a neighbour. And when you agree with her, saying oh that's terrible, they shouldn't have said that, or done that, she switches and suddenly defends them. "Oh, he's got psychological problems! It's not his fault, you can't blame him!" Essentially so she can portray herself as the defender of the world's misunderstood people - which she clearly considers herself to be. All the moaning is forgotten the moment she springs her little trap, cornering you into the unkind corner.
And I think a similar thing is happening to the OP. Her MIL is setting up dramas, but reserving a good role for herself, ie the kind person who's just been unkindly rebuffed or criticised. But of course many of the things she does are not kind by any stretch of the imagination. She wanted her son to move in with her & look after her while her DIL coped with 3 DCs immediately after major surgery!
The trouble with people who behave like this is, you can never level with them; you can't have an entirely honest conversation with them because their unmet needs are always front & centre, distorting everything. What made the difference for you was realising that your MIL was in fact trying to help, just going about it badly. But what if they're not trying to help? What if your interactions with them are just a charade of neediness and manipulation?
I've had to withdraw a long way from my MIL. When we visit, I behave more like a friendly repair man than anything else - because almost always, I'm fixing something for her. If she tries to trap me into being unkind or inconsiderate, I absolutely have to grey-rock. It's sad, but the conversations she wants & tries to have are meaningless, really. They're designed solely to deliver an emotional payoff to her, always at someone else's expense. So you have to behave as if the interaction you're having with her is the one YOU want. I keep things cheery, I don't respond to any bait-y comments, I change the subject. If things get too awful, I say, ok I'm going now, I'll be back when you're feeling a bit better. Shall I make you a tea before I go? Something like that - but I make it clear I'm going.
It's very much like dealing with a child behaving badly; you don't give them the payoff they're angling for - eg shouting, because of course that makes you the bad guy & justifies their crap behaviour.