Hi LJS0617,
I come at BPD from a different angle, my significant other (SO) has an undiagnosed BPD ex-wife (uBPDxw) and they share two daughters. So I don't have anything for you in terms of the double standards, but I did want to pop in and give you some information in terms of your kids.
He also has a good kid and a bad one. My son, 12ro is the bad... .his oldest daughter, 10yo is the good. He is very blind and insists he treats all things and kids the same. The kids have begun feeling unwelcome and not loved.
It sounds like your Husband is "Splitting" your children. This is not uncommon one child is the "Golden" Child who can do no wrong and the other is the "Scapegoat" Child who gets blamed for everything. Both are unhealthy for your children.
Link to more on Splitting... .
https://bpdfamily.com/message_board/index.php?topic=62033.0My SO's uBPDxw treated their oldest as her "Golden" Child... .Their relationship involved enmeshment and Parentification... .D14 was being told all of her mother's adult problems, she was her mom's "best friend", she was her mother's care taker, she was put in the role of her sister's care taker. Their younger Daughter was the "Scapegoat" she has poor self-esteem, is a people pleaser, struggles with boundaries, and was bullied by her mom and sister.
Below, is a link to the "Lesson" information from the co-parenting board you might want to take a look when you have the chance... .
https://bpdfamily.com/message_board/index.php?topic=182254.msg1331288#msg1331288Panda39