I am always confused why no one puts harmony-loving Charles in Hufflepuff though. Is it because he looks good in blue? He's smart but so was Hermione. What he values is harmony and loyalty. He'd not avaunt guard at all.
Honestly... your choices are perfect. Especially Steve - he might appear very brave (and definitely is), but why? Because he's helping and protecting others. There's no better example for showing that a Hufflepuff can be great than him. Charles and Tony both being Ravenclaws... makes sense. The two are very similar, so it would be weird to have them in different houses. Not to mention that they are the "nicer" smart guys (compared to Loki and Erik) As for Thor... there's nothing to say, because Thor being Gryffindor is pretty obvious.