Ive been lurking , i am horrified by your dh attitude in assuming you will care for baby and not attending her scan .
I think you will have to bow out to some extent , it sounds like he is going to have to be forced to take responsibility . I would not have any discussions about getting up in the night , caring for it while shes at school ect , and if i did it would be to say a firm No . I would have no further discussions until your dh is present and engaged in whats going on.
Id also consider working full time and having a prior apointment for the next scan / midwife visit or whatever . They are both being very unfair on you . If you can i would try to emotionally disengage for now . You really must start as you mean to go on , if you end up caring for this baby it wont be for a few months , it could potentially be for years .
I think you need to make it 100 per cent clear that you are not available for night time feeds , not willing to financially support them , you are not a free childminder . While you are worrying and planning your dh isnt having to , bollocks to that. You dont have to prove anything to anybody , its ok , and reasonable to make it clear that your role here will be very limited.