Does it mean that we can see Mr Kinnear's ranginess through his slouch said, his iago and his lines?
Are you parsing "his slouch said" as a noun phrase? It isn't.
Without further context, it could be parsed that way. English does sometimes allow modifiers to follow the nouns that they modify. However, that isn't a natural interpretation in this context.
"His slouch" means his curved posture. The verb "said" is used figuratively, and means something like "expressed" or "demonstrated". This use of "lines" is theatre jargon, and it means the collection of words written in the script that are meant to be spoken on stage.
The words that Mr. Kinnear uses on stage tell us something about the character that he plays. The posture that he uses on stage also tells us something about this character. We can get as much information about Iago from this actor's slouch as we can get from his lines.