As a dude, I know he's not interested. What you were seeing as flirts and winks, was likely him being friendly. He may have been curious at one time, but not anymore. Plus, reading his posts on FB going back several years is very bad behavior. You're probably putting out similar vibes in real life.
If you want him (and remember there's no sign he'll reciprocate) just keep an office friendly relationship. Say 'Hello' when needed, when he tries to strike up a conversation, end it politely (not rushed) and say as little as possible. If you do this, he may think you're over him and it'll either make him want you or you'll have a normal office relationship from there on out.