So your husband in your own words is “really stepping up” but also “having a tricky period at work” is “more stressed” and “emotional lately” to the point you worry about your DD noticing.
He is working then exclusively parenting one child and is obviously struggling and showing frustration and a lack of patience (which has been out of character for him in recent years) and he’s going against your ‘house rules’ by being unable to be a robot.
He is clearly struggling and then is criticised on a WhatsApp group by your sister for not staying awake all night - on top of everything else. Instead of defending him you agree with her and make it seem like you think the situation is “unfair” but under the guise it’s all a big joke.
Your husband gets upset and clearly shows his emotions and how much this comment hurt him and you “didn’t say a word” in response.
Instead of seeing that he’d broken down and was feeling unsupported and talking things through and seeing how you can fix things you booked a hotel room for you and your kids without telling him?!
If you put in your OP that you were the one who was stressed and worried and overheard your husband agreeing with his sister that you didn’t pull your weight and you lost your temper and “stomped about and kicked some toys” then I imagine people would be posting saying how you needed more support and a healthier way to communicate. If your husband then fucked off with the kids to a hotel you’d be told to LTB.
You sound like you are trying to punish your husband for having feelings and not doing things your way. If you take your kids and leave when he’s obviously feeling vulnerable then I think that’s pretty cold hearted, if you were genuinely worried scared of him then I think you’d have mentioned it in the OP.
I can’t help but think this is a really unhealthy approach and awful way to treat a man who seems to be trying his best and is under pressure. If you don’t care about your husband or marriage then crack on but the one throwing the tantrum is YOU.
Maybe I’ve misread the situation completely - who can tell from your OP that’s obviously biased?
Maybe your husband is a bad tempered arsehole who deserves punishment? But if for any reason you decide you’ve overreacted then please knock this plan on the head, you are putting your kids in the middle of the argument as well. Do you want your kids to think daddy deserves to be left at home on his own?
My dad was sometimes stressed and bad tempered and my mum often “joked” about “grumpy daddy” and said things like “let’s go and leave grumpy daddy at home and go out”. I found out as an adult he was deeply depressed and hated his job, my mum didn’t work and expected him to work 60 hours a week but then also to match her 50/50 with kids when he finished work, he was exhausted and resented it. Whatever parenting he did was wrong, I’m in my thirties but still remember my mums criticism and my dad’s defeated expression.
My mum basically had us take the piss out of his misery, we didn’t realise as we were kids. I HATED finding that out as I got older.
You are a family so start acting like it, if you can’t and it means separating from your husband then do that - but still treat each other with respect.
Please don’t let others comment on your marriage and judge it because no one is ever impartial unless you go for counselling and based on your OP I actually think that would be an excellent idea.
I feel like this is a situation that could be resolved by talking to each other and both being loving and supportive and finding ways to make each others lives easier. Your husband seems like a good man from your OP who seems to be trying to put the effort in but it appears he’s struggling with things and isn’t communicating them the right way, if you walk away now then you will likely damage your marriage forever. If you are also finding things difficult then talk him - without resorting to passive aggression.
Both of you need to stop the ‘Tantrums’ and start talking and listening, you are both BU and have both overreacted.