As regards the Han baiting Luke over whther he stood a chance with Leia, I'd say Marvel played it right. That was pretty much how the scene played when I first saw the movie back in 1978 (London, Leicester Square Odeon... in late January). It's only in retrospect with the other movies that it has anything like an ironic resonance.
Rememeber that Luke and Leia being siblings was one of Lucas' many, many rewrites of the story later on (Hence the really squicky kiss near the start of Empire), so at the point this was written, they were probably destined to be together or at least Han wasn't going to end up with her.