Seeking, Just wanted to let you know that my stbx does act odd towards me as well. Friendly, even jokingly, then akward and tense the next.
He went completely dark on me when I retained my own attorney, and he also didn't offer up anything on my proposals up until the day before court. Why? I have no idea. Your sitch raised questions of my own given they're similar.
However I didn't say a thing to him about his behavior and I do believe it's best that perhaps you do the same. If he wants to talk turkey he can contact you or do it through the attorneys. I agree he's conflicted and doesn't know what to do either.