Han should be jealous in ROTJ - it's actually a part of his character arc. He goes from acting like a tough mother I-don't-care attitude to actually wanting to settle down with a lady and talk about his feelings...

Most guys that act tough do so out of low self-esteem in the first place - he's only showing that he's able to deal with his feelings and take the high road "I won't stand in the way" instead of the typical tough-guy "Meh, I didn't care about you anyway..."

By being jealous, it shows he's matured... As odd as that sounds...