Pilot's advice to ask how he is doing is interesting. I always take the opposite approach. Maybe I've been doing that wrong!? Interesting! How I usually do it is stay upbeat and ask something like "how is it going in (new city)? Are you loving the (weather, traffic, whatever)?" Keeping it light and maybe making a small joke of it. Acting like nothing bothers me and I'm totally cool with the fact that he moved out.
I am not saying reopen communication altogether. I am saying you "seem' to have him at a moment of weakened emotional state where his thoughts are on you. I am advocating exploiting it. Basically one giant tease. A reminder to him of just how awesome you are. You can mix in sweet as well. Listen to him, validate him but by no means engage in any relationship talk. Just be a friend to him as you would a gf of yours caught in the same position. The only thing he should hear from you about you is just how absolutely awesome you are doing and how great things are. This is just a one time deal because of his expressed interest in you.
Maybe I am not articulating what I mean very well. You could always stay dark and NC. It is by far the safe move. But I guarantee this emotional state/concern for you will pass. Heck, it will prob pass no matter what you do. So why not show this starving man you are a prime filet perfectly cooked and let him look, savor, and drool over the steak he passed on when he was full. He certainly is not allowed to eat this steak right now. But you want him to part ways with you knowing what he used to have. Go and be everything he ever wanted in a woman (because you used to be just that) and then leave.
Me: 42 W: 32 Married 7 years together 8.5 S1: 7 S2:7 Bomb #1: 09-16-13 Recon #1: 11/13 A discovered 04-03-2014 W filed D 05-19-14 but never served me I filed D 12-02-2014 S 05-31-14 Divorced 5-19-16