I think that you've done everything you can short of begging. By now, he knows that you're interested. If he becomes available in the future, if he is also interested, he will undoubtedly contact you. I can't speak for him, but if I were in his shoes, I'd be turned off by any further solicitation. If he wanted you to pursue him, he would have shown it by now.

That's just my opinion. I prefer things to progress with mutual interest, with less force than you've shown.