He has always been a bit like this. Always right, expects perfect behaviour etc but it’s been manageable due to me mitigating and facilitating outside interests so we don’t spend much time at home with him. Family holidays are rare due to this behaviour as his lack of patience and sharp tongue always increase in those sort of situations. Right now though we have no escape from it do we? If I challenge it then it results in worse moods and silent treatment. He can’t be challenged because he’s always got an answer, always perfect and always right.
I had one like this. There are no strategies that work.
Actually, I misspoke. The strategy that works is divorce.
I am with the people who are asking why the children are too traumatised about covid 19 to sleep. Who told them about it in such a way that they are so frightened? I absolutely agree with SignGrudgeBluebook's thoughts on this topic.
However, I would also agree that what is really keeping them from sleep is the stress of living with your H. He is bullying them in their own home.
You have a choice here, and no matter how unpalatable the alternatives are, just knowing that you have the gumption to make a fundamental change could be exactly what your children need. Choosing not to put up with it any more will teach your children a lot about how you value them and yourself.
Take care, @notsuremate.

You need to stop right now this hoping that you can manage or mitigate or control this awful situation. Optimism is not your friend here. In fact, it's toxic.
You didn't cause what your H is doing. You can't control it. All you can do is anticipate fires and try to avoid them or run around putting out fires. There comes this point - hastened by the coronavirus - where you realise that your entire life revolves around dealing with the emotional and psychological chaos he creates. We are talking emotional and psychological abuse here of everyone in your home.
You can't cure this from within or heal your children while they are still living in the trenches.
Start figuring out how you can manage the big change that is needed here. Think of it in terms of project management. Buy and read (kindle is possibly best) the Lundy Bancroft book mentioned by a pp.
Visualise a better future.
Don't overthink what it will take to get there. Remember that the aim of abuse is to make the victim believe that she has no choice but to stay and be abused.