Your heart is in the right place, your concerned about your daughter 1st and not letting the way your ex treats you come before your daugthers well being. You have evry right to attend your daugthers events, you are her mother and you want to be there to support her. Don't let your ex control your thoughts when it comes to that. I know it's hard, very hard to control but others and our circumstances can and do effect our mood swings. Rest assured your thoughts are in the right place as for your daugther and not using your daugther as a way to hurt him the way your ex is doing to you.
As far as recording his phone calls I would not get into that, at least not yet, try to work it out with him 1st the way you are doing before you go to that extreme. If he is negeleting her and mistreating her in other ways that's different, but if this is the only matter then I would doubt if any judge would take custody away on that grounds. You are putting her (your daugthers) needs 1st because you think she benefits from him being in her life.
I also would be careful about getting third parties involed with matters and disagreements with your ex like you did with the director, I know this upset you and I know she offered to talk to him, but getting others involed in your family matters could end badly for you. He could tell her a bunch of lies to the director to try to turn her agaisnt you and side with him etc.