I think that “clouding your judgment” has a subjective definition, which could be massaged to refer to any action which involves risk in the name of fulfilling those ambitions. From your own perspective, ambition can’t obscure your judgment, it can only play a part in comprising it.
You don’t need that much blood (a pricked finger will do the trick in a pinch), thankfully. Antari banecasters will generally use their own, since they consider it more potent and more “pure” than that of a serf or a freeholder.
Hunter (like most Tierrans) is a bit less discerning. Blood is blood, and he got his from a surgeon.