@Whatisthisallabout1
I’m sorry about your miscarriage. It must have been hard. If your husband was not happy about the pregnancy, I suppose he wasn’t as affected by it as you were and that is perhaps not surprising. That does not excuse him being unkind or mocking you though, which is totally unacceptable, whatever his feelings about the pregnancy were.
That said, you aren’t being rational. I just don’t get your reasoning- you paint a picture of an unkind- and possibly abusive- husband, whom who you say you hate. But you still want to push him into having a child he does not want. Why would you want a baby with him, if what you say is true? Honestly, how do you see that working out for the children? And for you? I think this is absolutely not a situation you should aim to bring a child into.
If you are in a toxic or abusive relationship, you should absolutely not bring a child into that. You should be making plans to leave for own sake, and your daughter’s too. Or, you are exaggerating how bad he is, in which case you are potentially being manipulative in order to get what you want. Either way, you are not in a good place mentally and a baby is not going to magically fix everything in your life, however much you have convinced yourself that it will.
I think the truth is that you want another baby so much you are twisting all sorts of facts to fit your narrative. The nonsense about your daughter absolutely, 100% needing a sibling in order to be happy and well adjusted is exactly that- nonsense. Your daughter is not being deprived or damaged solely by virtue of being an only child. Your husband is not harming her by declining to have another baby with you. He really isn’t. The truth is you desperately want another baby and will hang onto any and all justifications for this.
Most only children are just fine, and if they aren’t it is usually nothing to do with their lack of sibling- it is because of the way they are parented and their home environment. Additionally, you argue your daughter must have a sibling for support. Sibling relationships can be wonderful. They can also be fraught with angst or active dislike. Or sometimes, indifferent. You have no guarantee your children will like each other or have any relationship at all, nor is there any way to anticipate if they will be supportive towards each other (with regards caring for you as you age, or anything else). With a large age gap, it is more likely than not that their relationship will be more distant (especially in childhood, as they will be such different life stages).
Leaving just to have another baby is not straightforward- at least, if you are doing it with any care towards your daughter’s well-being. By all means, end an unhappy or abusive marriage, but then you need to give your daughter time to adjust before you jump into introducing her to a new partner. Then you would have to give them time before living together and then giving that time to bed in before trying for another child. You can’t just leave, jump into a new relationship and be pregnant within months. Even if you decided to go down the sperm donor route, you’d still need to give your daughter time to adjust to the change in her family and to see how you manage as a single mum, before moving forward with that.
You need to take a step back, look at the situation and your marriage, decide whether you are in an abusive or unhappy marriage and if you are, then make plans to end it and move forward. Or, if your DH is not quite as you have painted him, and you do love him and the family you have created more than you desire another baby, then you need help to move past these feelings. It is clear that he does not want another baby, come what may, so you need to make peace with the fact you are not going to have a baby with him (willingly at least).