And your question occured me in the Snupin fic "Staffroom Seduction", Snape asked Lupin "Do you want me to stop calling you 'my dear little werewolf'?" It's not insult at all but full of affection, Lupin's answer just made me believe he loved to be called like this by Snape.
So as the same, you are writting your own story, create your own world, you make all rules how to play, control all the terms. Please don't worry too much about which to use. For me the most important thing is proper explain and make sense perfectly.
As to the soul, I prefer Remus knows both sides of himself even in the wolf form, never give up struggling. I think (in canon) he is strong, maybe the strongest one among his Gryffindor classmates, but for fanfics, everything up to the author
Er, in Chinese fandom community we just say "The Author makes Empire provision" :)