Sounds like he is up to the idea to file joint. I thought your response was well thought out and so was his.
If I was to draw a simple conclusion from that exchange i would say that he is moving away from anger and is starting to 'cool' off a little. I think the way you handle any exchanges with him is key and so far you are doing a good job of that.
This is simply logistics but none the less it is communication and I think that is good, Rome was not built in a day.
The most important thing is how you react to the exchanges if he feels comfortable when he reaches out he will reach out more. Remember he is far more detached than you are so as you go forward expect nothing from him. Treat every communication as your last and keep in mind that your goal is to allow him to hate the fact that he left you because you are the better option, only way to get to that point is to remain calm and focused
