Okay... what I got from all that was "Should I try and hook up with this guy I had this major thing for in high school?" I have 2 responses to that. I 'think' that the boyfriend you mentioned was the old guy's, not the young guy you are in interested in. If I'm wrong then moving forward with the intention of trying to get intimate would be wrong-you should never poach another man's man, imo. That doesn't preclude hanging out as friends though.
The second response is that life is freaking short. Why not meet up and keep an open mind about getting together, for a night or maybe more? So he doesn't live nearby ... that might change, you might move or he might, if things really took off. You never know and you won't know unless you give it a shot. At the very least you're reconnecting with what could be a good friend again, and even if nothing lasting comes of it, if you guys do hook up you have the fun from that at least, lol.