Maybe I'm the one with the problem?

Paula • Pregnant and so in love already ❤️
So, my husband has a child from a previous relationship. When we got together, she took it bad, she obviously still loved him very much. I was fully aware of that and tried to keep everything low key. He proposed and I said we shouldn't out it on Facebook, that is until she text him because of a photo I put on. I didn't think, but I put a picture on saying "my boyz ✌🏻"(stupid I know 😩 didn't think about it till after, they both had baseball caps and sunnies on) Anyway, since then she had a massive issue with me. I fell pregnant, had a boy, I called round to her house and tried to make it right, I thought we had but obviously not! 
I have serious issues with her parenting; 
- he's six, he sleeps in her bed doesn't go to bed till 11, when I say he sleeps, he doesn't sleep, he sleeps better in his own bed. He was so tired he was an emotional wreck! He cried every day we had him (obviously, refreshed when she got him, because he had a good night sleep!) School had mentioned something, but blamed my new born son! I understand that it has some effect on children, but he dotes on my son! 
- She tries to be his be his best friend, not his mum. He has no boundaries when he's with her, he totally changes when he's with her. You can see it in his face. 
- she has another child from a previous relationship and again, he never had any boundaries, it's one step away from social services, Seth (my husbands son with her) came and as soon as I saw him he burst in to tears and said 'my mum said she has had enough with life' he's FUCKING 6!!! Ho does he know this sort of shit! 
- She was having problems with his behaviour, shand told my husband we can only have him on a weekend (we have him 50/50)
- even though custody is 50/50 she asked for maintenance money! We buy most of his clothes, hair cuts (she said to Seth that his dad can pay) IF she got maintenance money she would get £7 per week because my husband doesn't work much, I told her we can stop buying clothes and just give her £7 a week, that's fine! She soon changed her mind!
- I opened a bank account for him, she insisted that her name was on his account! I don't think so! She already 'borrows' money out of his money box! 
- She tells him we should pay for him to go places, in on £139 per week maternity pay, my husband earns £80.... we can't afford to spend loads, we do things for free, go for walks etc! 
My husbands family kiss the ground she walks on, she has them wrapped around their little finger! She is so manipulative. She is 48, my husband 33.... because of his crap mother, he was looking for a mother figure, not someone to trap him. 
We had a family photo shoot with all of the kids, his sister created a FB group to put all of the photos in. Then wanted to add her so she could see the photos, I asked his sister to remove the pictures of my son and that's fine. All of his family have kicked off, I'm sorry,but she has nothing to do with Noah, she is poison!!! 
Is it me? Am I in the wrong? Do I need to sort myself out?