Thank you for reading this long entry... but please tell me: what I did I do wrong?

Well I see this two ways. On the optimistic side, he's a really shy guy and really messed up trying to play hard to get by really showing you he liked you and still trying to do the whole cliche' 'act as if you don't care' thing. It's a common mistake amongst us male folk :-) On a more pessimistic note he possibly could have gotten a girlfriend after thinking that you weren't interested, and then when you said that you were he felt really bad but didn't know how to tell you, though I'm more inclined to say he just really screwed up his punchline. Good luck, and he really does sound like a sweet guy, not many will look at a girl with respect instead of that creepy pre- glare that is all too common.