Sympathies op, this situation sounds like an absolute nightmare and your ex sounds like he is immature, selfish, manipulative, disrespectful and a terrible parent.
With regards to your ex, you can’t control his actions, you can only control your reaction to him and this situation, and if you continue to be a consistent, sensible, kind, parent who is well regulated in terms of emotion, who is fair, reasonable, loving and open with communication, and you show love and respect to your dd, then don’t worry, your dd will eventually see the light.
So I would encourage you to keep your counsel. Grey rock your ex and keep communication with him to an absolute minimum. Communicate through a third party (not your dd) if you have to, Or have one phone or one WhatsApp account where all of your communication with him happens. Stick to clear, short messages with minimal emotion or detail. Don’t allow him to ring you up any time except in an emergency, Send one message a week on a Sunday morning to confirm arrangements for the week ahead.
Don’t allow him to occupy too much of your head space or take too much of your energy. The more traction you give him, the more he will make mischief.
Don’t bad mouth him in front of your dd. Be professional and neutral.
I know that is easier said than done when it feels like he is turning your dd against you, but the more you respond with alarm, anxiety, despair, the more he wins!
So give the impression at least, of not being particular perturbed, keep very calm, imagine a radio where you turn his voice right down so it can barely be heard, focus on your own life, and try and act strong, confident, cheerful, positive and be a great role model for your dd.
Hold your boundaries at home but pick your battles and be very loving towards your dd. Do not let this issue with your ex encroach on your relationship with her and certainly don’t resent or blame her for listening to her dad so much. She is absolutely desperate for his love but unfortunately she will find out in time what he is really like.
When she pushes back and says, “but dad says” just ignore that and quietly say, “what do you think?” Or “that’s fine, I prefer to do it this way because of x, y, z” or “that’s fine but doing well in this exam will give you more choices, it’s up to you, I want the very best for you.”
“But dad says the school is crap!”
“That’s fine but my belief is that …because of ,., (concrete example) what do you think?”
Dial down the conflict.
Hard though it is, do not let your dd occupy the middle space between you and your ex. Try and keep your relationship with her exclusive. In other words, don’t let the majority of your interactions with her be reactive ones to whatever your ex is doing, Ignore him as much as possible and take the initiative and make sure your dd and you have special things you do together
Also remember that “some* of your DD’s rebellion towards you will be nothing to do with your ex and just because she is a normal teenager trying to push boundaries, and that part of her, will eventually come back to you and she will return to being her usual pleasant self and appreciating everything you have done for her! So please don’t despair and hold strong.
It’s very normal that she has to challenge and reject you and your values for a while in order to individuate and become an adult and her own person.. Whatever you do, do not take this personally. The more bonded with you they are, the more force they have to use to push themselves off in to adulthood.
Focus on your own life, your job, your friends and hobbies. Let your dd see you enjoying life and your interests. Create a calm space for your both at home. It’s so tough op, but hang in there, stick to what you know is right for your dd, keep quietly plugging away being there for her and ignoring your ex as much as possible.
Give him minimal information about your life. He has no say in the sale of your late dad’s house for example. It’s nothing to do with him. Shut him down with a calm “that’s my business thanks” like you are not bothered.
Once you close your front door behind you, and your dd is inside, don’t allow your ex to encroach upon that space. And maybe insist that you only communicate by text with your dd when she is at his house. She can ring you any time but it has to he a private conversation. Don’t be drawn in to his dramas.
Completely separate from your ex, if your DD’s complaint is that you are too controlling, then that is your cue to step back a bit and give her more responsibility.
Stick to your chosen battles and boundaries but now is the time to adapt your parenting style now she is older, Let your parenting be more collaborative, parent alongside her, rather than top down (except if she is in actual danger). Ask her opinion, talk through choices. Agree on compromises and strategies whereby she can earn your trust. The more trust she earns, the more freedom she gets.
Encourage her to cook meals, be responsible for a food shop, she can start doing her own laundry? Put her in situations which are a little above her competence level, like trying to negotiate a lower price at a car boot sale. Go out for dinner at a fancy restaurant together. Give her a week’s household budget and ask har to manage it. If you can, bring her to your work and show her the ropes.
Keep strong 💪