It's been a while, hasn't it? Updates, I mean.
Anyway, first off: dialogue. You keep inserting these little foreign expressions, but the rest of it is straight American English. As a result, I stumble every time I see a "non," or a "perdon." If you only want to use a few easily translatable foreign words, that's fine, but change the phrasing of the rest so that we know the speakers aren't native. Otherwise, just lose the foreign interjections, and we'll assume from the names that the setting is foreign and they're speaking in their native language, conveniently transliterated for us readers.
I'm still a little confused about how humors work, exactly. You've mentioned colors and physical sensations both, but I'm not sure how those combine to create different personality traits, talents or skills, and physical appearances. For example, you've mentioned both fighters and merchants usually have red humors, but that the Maestro is mostly yellow. It would make sense for Mathieu to wonder (or speculate, if he's come across something similar in the wars), right there, about how qualities common to yellow humors would impact the effectiveness of a fighter, or trainer, right there while we're still talking to him- and incidentally, also informing the reader of the differences.
I would think, coming from a poor background, that Mathieu would be a little more reluctant (or suspicious, or even inquisitive to the point of rudeness) to let such a large sum of money go into the hands of someone who he doesn't personally know, and who deals in risky but lucrative trading, emphasis on the risk. The whole exchange comes across as the wolf fleecing the young and tender lamb. Sure, the lamb will be tougher the next time around, but he'll still be short one fleece. And, on top of that, for him to turn right around and contemplate spending yet more money sleeping with his best friend? When he's already worried about how little he has to live on? Yeah, I'm gonna need a little more active motivation. Even the fact that the Mistress of the House wouldn't let Cassandra spend time with anyone (particularly a male) without money up front would be enough.