I am with you on almost all of these, except that I think Angel is Slytherin. Partly because he's a little lazy for a Ravenclaw (more before he becomes a vampire, but still), and he does think of things in terms of who has power over whom, whether he's got his soul or not.

And I think Spike is a Hufflepuff with a Gryffindor kink trying to pretend he's a Slytherin because he thinks it makes him seem more evil and badass. He's deeply loyal and a secret romantic who loves grand, bold, possibly suicidal gestures, you know? He tries to pretend he cares about power and manipulation, but he really doesn't.