It seems that many MLCs have a trigger, on top of age... I'd say that sure looks like the case here!
It sounds to me like you are doing pretty well. I don't think you can force the issue on the OW right now, I think he would just run to her if you did. On the other hand, I think it looks like he is already seeing that she isn't "all that". Maybe even sooner than you could have hoped.
The only thing I would say right now is that trying to decode his actions right now isn't going to do anything but give you a headache. I think right now patience is your friend.
