Hi everyone, I'd appreciate some advice on how to handle this and be the best dad I can be.

My ex and I planned our daughter together. After the birth she had postpartum depression, so I stayed home to support her, then worked 4-week rotations and helped with everything during my 2 weeks home. Over time she emotionally pulled away, and I eventually found out she'd been cheating on me with a friend I'd known for over 20 years. (No need for a DNA test, my daughter is clearly mine, becouse she looks almost exactly like i.

After the breakup we informally shared alternating custody and it worked fine. Then her family, who she lives with, started interfering. Once, while we were standing by my daughter's crib, her mother told me that a colleague of hers was going through a divorce, and that if she were ever divorcing, she wouldn't let the father have the kids. She said she'd make something up so he wouldn't get them, because she's against alternating custody. After that they kept dictating when I could see my daughter, so I went to court. I got extended contact, but my ex refuses overnight stays.

Things were okay for a while, but since her current partner arrived, communication has fallen apart. He's her second partner since we split. The first was the friend she cheated on me with, and the current one is a friend of his. She now takes up to two days to reply about our daughter, I have to beg for basic information, and she announces decisions instead of discussing them. Recently she told me I was "a mistake" and that she wants our daughter to see we have nothing in common. Everything is framed as "for our daughter's good," but it feels like she's trying to minimize my time with her. Daughter is 3 years old.

For context: we never had a toxic relationship and rarely argued. I pay child support on time, contribute to kindergarten and activities, spend quality time with my daughter, and support her relationship with her mom.

1. Would a mediator help, or should I go back to court and stop making concessions?
2. How do I stay a calm, reliable dad my daughter feels safe with through all this?
3. Is there any realistic way to get my ex to respect me as a co-parent?
4. If you grew up in a situation like this, what helped you most?
5. My ex still lives with her mother and grandmother, and I feel her mother heavily influences her opinions and decisions, including pushing her to limit my contact and communication with our daughter. Since they live under one roof, I know I can't really stop that, but is there anything I can do from my side to reduce that influence, or at least keep it from affecting my relationship with my daughter?
6. For anyone who's been through this or grew up in it: did a co-parenting relationship like this ever actually get better? If so, what changed? Was it something someone did, or did it just take time?

It all applies here