to an extent, I wonder if any sequel could have satisfied your needs. unfortunately, that's the need of a story--to continue the world and answer questions and all that. there's no way the mystery of Star Wars could live once you continue the story past that first film, because to tell a story, you HAVE to eliminate some mystery. i can understand where you're coming from there, and if I didn't like empire, i'd probably feel the same way. (i kinda feel that way about the matrix films, actually.)
re: han--i think his character in the second film is perfectly set up by the first film. he decides to leave, then has second thoughts because (i think) he starts to feel as though he should get involved with this rebellion and that he can't hide from the oppression of the empire and not do anything about it. and he may have assumed a military role between ANH and ESB, but empire finds him wanting to get out of that role--the only thing that keeps him in the mix is running from the empire, then leia. (now as to why he sticks around after being unfrozen from carbonite in ROTJ...who knows.)
story-wise, I think it is the least polished and least clean of any of the SW films. everything goes very WRONG. that's easy to take for granted now that the movie's 25 years old, but that's always struck me as such a ballsy and fierce move. the bad guys win. luke makes a bad decision on his training and faces vader too soon. han's in carbonite. leia, who has now fallen for him, is left alone. lando betrays them. even threepio is shattered to pieces. i certainly don't see that as "polished" or "clean."
and actually, i think that visual motif of your favorite shot of luke hanging on to the weather vane is echoed throughout--the desolation of hoth, the way the AT-ATs dwarf the rebels, the miniscule millennium falcon against the asteroids and star destroyers. it all underlines that sense of failure, of losing, of being overtaken by events and a staggering, massive Empire.