Well, I'm not sure if I understand, but I think it would be important for your child not to have his/her father think of him/her as second best. Of course, with all the paperwork and emotions and cost involved with pursuing an adoption, I would guess your husband would be on board with this or it wouldn't work. So he would consider your child together as his, too, right? I'm not really getting that from your post.
I guess I could understand your husband putting his children before you (in a sense), but not his ex before you or his bio children before his adopted children.
There are plenty of people who have extended family who are not keen on their adopted children. The parents just shield their children from these relatives. But I think it would be hard on a child to have a father who thinks of him/her as "less." Many adopted children have issues as it is, and it's important their adoptive parents love them unconditionally.
I don't mean to put a damper on your plans, but I do feel it's important that any child you have (adopted or bio) be fully accepted by your husband. Honestly, I wouldn't want to bring a child into a relationship where you aren't valued. I don't want to advocate divorce and your marriage as such is none of my business, but since you are asking for our opinions, I believe your child might be better in a single parent family than in a family where the father isn't 100% enthusiastic, head over heels in love with your (and his) child. I just have to be honest about that. While having a child might fulfill you, you are asking for heartache for your child; and, someday, you will grieve when you see your child hurting because your love for your child will overshadow anything you are feeling now. I would carefully consider my options before proceeding, and keep in mind that singles may adopt in the US and from many countries, too. Your age will not be a problem for you.
I sure hope you can find a solution that makes you happy and your child happy. I know about wanting a child so much it hurts. Good luck!