I think if you put aside this jealousy towards his daughter and try to have some compasion for them, then things will get smoother!
Honesty, this is my personal experience....If I feel jealous, which is happening often in a relationship and ruining my relationship, then everything goes back...
Think about her as a poor kid who has her parents being divorced...and think about him as a poor dad who is carring a guilt feelings over years....
Guys usually favour their daughter over their sons....that's very natural...nothing wrong with it at all....I think your husband has lots of guilt feelings and he thinks you and your kids have him already and don't need his attention as much as your step daughter needs....
However, if you start creating compasion towards both of them and try to see good stuff in them, life will be easier for you....You can't change them, but you can change yourself...you can change the way that you think about situation and the way that you behave!
I know this is easy to say, but you can practise it little by little and see the resault....

take care
Marjan

P.S. by the way...welcome to PC...you will find good friends here