I think you did reasonably well
Ideally, you'd be so okay with it that you wouldn't even think about it. The next best might have been saying: "ok, have more time", and then seething in privacy... and when he'd come home you'd tell him how it had made you feel and ask him to manage it better next time. But you're only learning, so your reaction is understandable, and what I think you really handled well, was that you suggested they take time to talk it through, AND you texted your partner's lover personally to reassure her - well done.
As for your partner's reactions, they are understandable too. His mistake was losing track of time. Ideally, he would have shown you the respect you deserve by planning things out a bit, to be able to have the dinner with you. But for some people (and gender stereotypes tend to say this is more common with men) once they get past that certain point, their sexual desire takes over their mental abilities and they become less emphatic.
Again, how the situation turned out is a great progress, and I congratulate you on dealing with it as you do.