I say this with love..
He is being a complete moron. I have nothing productive to say aside from the advice that others have given you.
I'm really not understanding why his bio child is more of a priority than your other children. Interesting that if you choose to treat your DSD as "less" than your own, it would be a deal breaker for him. It's great that he loves his daughter but your other children deserve just as much. I just don't understand where his head is at with regard to the new baby.
Unfortunately, you weren't around during hour DSDs conception or infancy and she isn't your child - if she were then she would have been raised the same. All of these choices that he and is ex made with regard to their parenting many years ago were simply not your choice and to put it bluntly, not your problem. He needs to be more adaptable and in turn you'll ensure he is included with this new baby. Should he not change his attitude it'll likely be a case of split family again and just IMO, it will be his fault.