Yusuke - 5, he puts in little effort, avoiding pain like a 7, then he finally realizes that he needs to push through, stop slacking and protect his friends like an 8. He also refuses to show emotion, doesn't even want keiko to know what's going on in his life.
Keiko - 4, based on lines on integration and disintegration. under stress, she acts like a 2 (clingy, feels abandoned), when relaxed, she acts like a 1. Also fits some 4 descriptions.
Kuwabara - 7, Though he could be a 3 because I have trouble telling them apart sometimes. I doubt that a 3 would have a soft spot like his, or the morality he exhibits, which I suspect comes from 7's disintegration to 1. I'm betting that later in the series, he'll start practicing his swordplay (integration to 5) AKA: preparation.
Kurama - 5, You instantly think 5, but then he mentions this while with Koenma watching a fight : "I don't belong here, Voyeurism has never been my strength", then he get's there.... and observes from the shadows.
Yukina - 9, Spends all of her time thinking about others, feels that she isn't worth their help and feels that they will be used up. Classic 9, right there
Still thinking about the others, I have ideas, but nothing concrete. I'll just update it sometime.