Islam, if it's true what they say about not requiring the hijab, does not come first for your husband. His interpretation of it or his family's interpretation of it or the mosque interpretation of it, comes first. If he's being contradictory to the teachings, Islam does not come first for him and neither do you or your daughter.
You can't excuse his behaviour because you think he's a good person. A good person would hear what you're saying, research, assess and cooperate. Not threaten you on the basis of incorrect information.
So, either the religion or the culture or both, require you to cover up and will require your daughter to so so, also. You have told us those are the facts. We are saying you don't have to put up with it. You don't have to pretend to be Islamic, you don't have to capitulate to the demands, you don't have to pretend he's a great person etc. You are in the UK. It is not an Islamic state here. Use your courage, your rights, the resources available and get out of a situation that is wrong for you and your children.
If you were okay with it, you wouldn't be here. Now, you see many of us see what you see, no need to doubt yourself. Do what you need to do.
Edited to say: as I said before, the hijab is always "optional" until it's not. Many things are presented as "optional" when you're first inducted into the religion and the noose tightens. Many will say this is not true of Islam but it is, from experience in my own family, so no one can contradict my experience with any degree of knowledge or authority.