Too hot or too cold?

if he is, then all the normal approaches to any given situation go out the window.

Your behaviour (action, approach, reaction) needs to change.

That is if you decide he's worth your effort.

This sounds like it about more than the temperature that time. 19 would be lower than most people like it (fine for me) 23 would be a bit higher. You came in hot and sweating, he came in chilly. So neither of you are right or wrong.
I wonder though if you are the sort of person who jumps in all the time with statements like those biscuits arent for eating, you need to sort the garden this weekend, I've put your blue shirt out for tonight...you know, a bit bossy. Maybe he's had enough and thinks Who made you the boss?
Without knowing your history it sounds an over reaction. Tbf though, if he was cold a quick extra blast would have helped and you could have undressed (and showered) and would have cooled down quickly enough. You could have then compromised on 21degrees

Yes we do have bigger problems and almost split before Christmas.
You need to revisit why you wanted to split because this is not to do with the heating at all. Honestly though, he was spoiling for a fight (as noted by him being a twat over the dog lead) and guess what, you had one. You handed him the excuse for it on a golden plate.

You wouldn't like my house then...😬

Yeah, this isn't about the heating. You basically just don't like each other.

But he's allowed to do things that make you unhappy. And if he doesn't appear happy to you, that's allowed too. He is allowed to say things that aren't true, and things that don't appear to be true. He can do whatever he likes, as long as it's legal.

If you don't want to be with someone who blows up at you, that's up to you to arrange for yourself. It's not up to someone who blows up to amend their behaviour to suit what you want. Take responsibility for yourself.

Oh so he also belittles and invalidates your emotions...

"You're crying for nothing...." you were obviously crying because you were emotionally hurt...

Not only did he belittle your emptions, he also shouted after you as you were leaving to belittle your emotions...

Have you considered this man is a narcissist?

Belittle your emotions
Accusation of its your fault
Gaslighting?
Lack of empathy
Manipulate situations to their end
Always a victim

Clearly there are wider issues between you than the temperature thing, but I'm not wading in to them, and instead sticking to the temperature disagreement.

In my opinion, where there's a disagreement about temperature, it should come down to how hard it is for each "side" to work around the issues if the decision goes the other way. So:

• if he's wearing only a t-shirt, he can easily work around being cold by putting on a jumper. So the heating shouldn't be going on.
• if he's cold despite being wrapped up warm, and you being too hot is only temporary because you've been exercising, then you easily work around that by going outside without your jacket on for 30 seconds. So the heating should be going on

That it is always him in the wrong

That's fine if he thinks that, but why would he stay in a relationship where he felt like that?

You are both being treated in ways that make you unhappy, and blaming the other rather than taking responsibility for your own happiness.

Grow up. He wasn't put here to make you happy. You weren't put here to make him happy. Choose company that makes you happy, and walk away from people who don't.

It's unreasonable that he's still angry hours later. I can honestly say that me and DH can have an argument, then it's forgotten within a few hours at most.
In this situation I wouldn't have thought turning the heating up would have given him the instant 'thaw out' heat that he wanted anyway. I usually put the fire on in the living room and we all sit in there for a bit if we've been out in the cold and need some instant heat. I do think it's unreasonable to turn the heating off if the house still feels cold though.

I think you would be much, much happier without him.

Whatever this argument is about, it's not just the heating. If he had turned it up and you had turned it down without discussing, I would have said you were unreasonable. But you asked, a reasonable basis to start a conversation, and he exploded. The response could have been that he was absolutely freezing, so wanted to keep it on to warm up, without the tantrum. A negotiation that it stays on for half hour, gets changed to 21, you pop out etc were all valid discussion potential.

he shouted after me I was crying for nothing

He's belittling your feelings... how can you stay with someone who does this?

So you think that the house should be at the temperature you like, due to your discomfort, regardless of the discomfort of anybody else?

From your update he sounds like a moody teenager.

YABVU and incredibly selfish. If I've been out in the cold I can feel it all the way to my bones and it causes me a huge amount of pain. I'm not saying he was in any pain, but the point is that it takes a long time to actually warm up through to your core, and just putting on layers is not enough.

He has been on good behaviour lately

Like a little boy? Don't you want a relationship with an adult, who behaves like an adult? Don't you want to be an adult?