I think you held up very well under difficult circumstances. I think your daughter did as well. I think your ex was horrible. To talk about new guy in this situation and to rub D's behaviour in your face (even when D was behaving well) was terribly inappropriate. But you can't control Ex's behaviour - you could only control your own (how many times have you heard that here?). But you did control your behaviour. And you set a great example to your daughter. You showed her that even when our loved ones occasionally screw up - we will stand beside them. We will support them. And we still love them.
Getting the low number. Giving up the seats you saved. Holding the doors etc - that was chivalrous behaviour and even if ex didn't seem to appreciate - she noticed.
Actions speak louder than words. Your actions spoke very loudly today.
I'm proud of you! But you can be extremely proud of yourself. And I will bet that things improve immensely with your daughter after this.