Georgia, Just leave him be. Could he be projecting on to you the fact that he was emotionally unavailable to you instead of the other way around? There are times when they project on to us what they have actually done or thinking of doing.
If you are pleasant and say hi or goodbye and just discuss the children, then you are doing what you need to do. If you want to try something different, wish him a nice day (with a smile) and walk out the door. He's still trying to find his way and most likely if you were to attempt to chat him up, he would not tell you much and be paranoid that you are now acting differently and think you are quizzing him.
Laugher is something you won't hear from the mlcer for a long time. They are in depression and they have to have that anger close to the surface in order to around us for any length of time. If their masks slip and they begin to thaw out their hearts and souls just a wee bit, they'll quickly disappear and have to go back into deep freeze because they can't be nice to us, it's not the way of the crisis individual.
Even though you are going out of town for work, travel safely and try to enjoy your time away.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.