I pray that your sit. will get better. Maybe if he wants more time with your youngest dd, you can somehow negotiate some more time with other dd-s. Nothing set in stone, but just see if he will let you have them a bit more once in a while. I don't think saying if you are going to have dd more then I want the other dd-s more will work. Instead if he wants to see dd, let him politely, compliment him on wanting to see her. Then a few days later see if he will let you do something with the other dd-s.
Make sure your PMA is up before you ask him, so you can stay upbeat and positive no matter what the out come. I just know in my situation the more I refrain from being negative with my XW the better we get along. Many times I have to bite my tongue to keep the peace and it doesn't seem fair.
This is difficult because the WAS-s don't have a sense of what is fair, so we always have to be very careful on how we approach our wants to them.
Jo, we are all pulling for you to have more time with your dd-s.