Insane exes and step kids

Ashlea • 27 years old... Married the love of my life 5.20.15 and gained 3 amazing step kids, baby #1 due May 2017
So my husband and I have been married for almost a year now, he has 3 kids with an ex girlfriend who is insane! My middle stepchild constantly states how she feels like she doesn't exist, her mother tells people how she's a loner and prefers to sit in her room and just read... While she does enjoy reading, she hates being alone, she wants to play, snuggle, help cook dinner and basically be up your butt 24/7, which is fine, I try to make sure I give her the time she wants because I know she doesn't get it with her mother. The oldest, does more than she should at her mothers, taking care of the youngest, getting him changed and watching him through the day, her mother claims she's a social butterfly who hates to read but she will sit and read a whole book in 3 hours or sit on the couch with me and want to read together and more and more lately she has been asking why she can't just stay with me and her father and then the poor youngest, at his mothers he is given a cell phone that is only hooked to the Internet to play games on to "let mommy and her boyfriend have adult time", he's also started crying frequently saying mommy needs to be at my house because mommy tells him that she needs to be there and it makes her mad when he leaves her and that mommys boyfriend gets mad at him at night when he wants mommy and gives him his cellphone and tells him to shut up and go to bed that mommy is his... Their mother let her new boyfriend move in with them over 3 months ago and since then the oldest two have started doing poorly in school and lying a lot, not bringing home their homework, saying they have none, not turning in what we do together, they are with us for less than 2 hours after school everyday and I sit down with them both, go through their book Bags to make sure they aren't forgetting anything or lying but if it's not in there we can't make them do it, my husband and I have contacted their teachers to try to figure out ways to help them approve and new lies come up, oh we only have to do half the page we are doing the other half in school tomorrow and so on. Well the oldest hide progress reports from us and the mother found them and is now planning to take us back to court because it's all our fault she's failing and it is obvious that it is in the kids best interest to be with her, who leaves in the morning before the kids even get up, making my mother in law come over to get them to school because she lied to the judge saying she works later than she does so my husband couldn't have them more and doesn't get home until after dinner, so she can get more child support, which she already gets a bit of plus other government support and she's the only one who can claim all three kids on taxes...She claims she just found the reports today but they have been in the bookbag since Thursday, which they weren't I went through the the book bag Thursday and this was the first day we had seen the kids since them and of course it's the one day I don't check the oldests bookbag... Why if you are so on top of her homework like you suddenly claim to be, despite the fact that both kids have said you have never talked about their homework or helped them when they had more than they could get done here because they get home eat a second dinner and then are sent to bed no later than 6:30-7, have you just found them now when they were with you all weekend? And how is our fault that the kids started lying and doing poorly after you let a stranger move in with them? It sucks because my husband is so affraid with all her lying and manipulating that she will somehow be able to take the kids from him that he won't fight her on anything, he won't take her back to court for breaking their agreement numerous times, to get it straightened out how much we actually have them in comparison to what she lied about, nothing and I'm at my breaking point here and don't know what to do anymore!!