Some mothers days I have my DDs here, some I have SS and my youngest DD some I have none of them. No matter which it is I will have a moment in the day were they all acknowledge me in some way. Then I see my own mother and MIL. I'm not sure what your expectations are you have a baby? So it isnt what you expect your child to do but actually that you expect your dp to give you his full undivided attention? I assume though that means your child his undivided attention also which then actually isn't about you at all. It is perfectly possible that he would have his dad and your son and leave you to have a lie in, read a book make you lunch what ever it is that you feel would make you feel appreciated. It happens in houses all around the world were there is more than one child in the family.
I always read your posts and in every one the sentiment and feeling I get from them is you tolerate your dsd and feel like you are doing your DP a favour in allowing him to have her as much as he does, along with the over riding feeling that you him and your ds are your little family and she's an inconvenience to that. Ultimately one that you wish didn't exist.
So it isnt the senario you want advice on but the validation that those feelings you have are OK. I personally don't think they are if you want a healthy and happy relationship. I wouldn't be married to Dh if that is how he felt about my dd and he wouldn't be married to me if I felt like that about his son.
When I read your posts they come across and quite petty and jealous of the fact your dp has another child. That is beyond being annoyed at schedule changing etc. Its an embedded feeling that will taint how your approach anything to do your dsd and his relationship with her.
You say he chose to have a child with some one he didn't love there for bringing stress into his life yet lack the ability to see you chose to have a child with someone who already had one therefore doing the exact same thing you want your dp to recognise and be grateful for you tolerating.
No matter how much you wish or play pretend your child is his second and there is another child in your immediate family unit and posting on here won't change that.
Its like he is being set up to fail and you are hell bent on making him pick you and your child that you see in competition with his older one. To be honest reading your posts and the themes behind them I understand why he is defensive and I would be to. I wouldn't want to live in a house with someone who tolerates my child the way you seem to from your posts.
You come across obsessed with the firsts he has or hasn't done with his older child its like a competition.
Honestly get some counselling work through the resentment you have that your family unit isn't the one you had imagined for yourself but did choose.
Get your DP to go and see if you can build a family that you both can actually be happy in with your partner, your dsd and your child. If you can't sit down and talk it through the two of you.
If not break up move on with your life but the grass may not be greener being the resident parent and trying to bring up your child in a seperated family and then you being the person bringing a child into another relationship but it might give you another perspective to the one you have now.