The issue here is purely one revolving around control. I grew up in a very similar environment and it’s toxic for everybody involved.
You said that his behaviour worsened during Covid and this is typical of households where one member acts like they get to dictate all rules around.
He is a teacher and probably misses the validating behaviour of correcting his pupils’ actions, behaviours etc and you are now experiencing it more intensely.
I would add that having meals together as a family and chatting to one another is a positive thing, but not if good manners just become yet another thing your husband scrutinises and corrects and punishes (verbally or otherwise).
Before Covid I worked and commuted long hours and as soon as I was through the door I would shower and get changed into comfortable loungewear. This is not incompatible with good parenting or with manners.
I would also like to ask if he pulls his weight around the house? A lot of men I know who say things like that have little experience of what it’s like to be dealing with cooking and dirty dishes and running around the children at the same time, so it wouldn’t surprise me in the least that he doesn’t see the benefit of wearing non-work or simply comfortable, cheap clothes at home.
I think you need to start a conversation about perspective and respect.
For him jeans and a sweater are comfortable. For you jeans aren’t comfortable enough and you prefer something stretchy and soft. If he doesn’t see or respect your point, I’m sorry to say that he is just being controlling and you must not give in at all otherwise it will be the thin end of the wedge.
Good luck!