try not to say keep in touch...its like asking him for attention. And his response...keep those calls, letters, rolling in! That's BS...almost like he is counting on the fact that you will keep up with the pursuing contact. Can't let him have that in the back of his mind as a "safety".
See how he pursued asking you where you were going, and again? He is intrigued, interested. Next time come back with something vague, mysterious..."oh, just of for a little adventure", or "Just for a little fun". Don't mention you are meeting a girl friend...let him wonder.
You've got the right idea. Its all in the execution. Believe me, I know. When I interact with my H, I analzye it later and see how close I was to on the right track, but tend to give myself away at the end by asking if he want's to get together again, or bordering too close on R talk...its sooooooooo hard to maintain the aloofness when you are talking to your former best friend. Believe me, I know.
Still try to have a great weekend and know that he will be wondering about the fun you are having.
Me 30 H 33 together:10 years married:5 years Separated: 1/23/09 living apart 5 mos and counting "when you reach the end of your rope, tie a knot and hang on"-FDR