Do the Bodhisattva Vows...clearly allow the practitioner to break the precepts occasionally...?
Yes. Precepts are not rigid laws or commandments; they're exemplars; the archetype of how a bodhisattva operates. We operate in the saha world; where real life is not black and white, but infinite gradients of gray. Sometimes we're faced with conundrums for which there simply are no good options, only least bad ones. What option best promotes and maintains ahimsa
; "non-harming"? Which option is most consistent with my vow to liberate all beings? What choice best inures to the welfare of all, no matter how imperfectly?
There's a story told of an exemplary monk beyond reproach, who awoke to find a naked woman in his bed. In great anguish, she said her child was very ill, perhaps terminally so, and that for sport the richest merchant in town promised to provide her child with the best medical care in the world if she could entice the monk to forsake his vows. Without hesitation the monk had sex with her, with great compassion and loving kindness. When the abbot found out, he publicly humiliated the monk and banished him; out of respect for the woman and to protect her from further suffering, the monk offered no defense. The sangha as a whole, who knew of the true facts of the case, came to his defense and persuaded the abbot to relent.
One of the Jataka Tales tells of a previous incarnation of the Buddha as a sea captain, who discovers that there is a murderous pirate on board, intent upon robbing and killing his passengers. He could either do nothing, in which case the passengers would all be killed, or he could expose the pirate for what he is, in which case the passengers would kill him first. He chose to kill the pirate himself, thereby not only saving the passengers lives, but saving them from the karmic consequences of killing the pirate. and conversely saving the pirate from the karmic consequences of killing the passengers. To save all beings, he chose to accept the karmic debt of killing himself.
In the Lotus Sutra, to entice the distracted children (us) from the burning house (samsaric world), the father (the Buddha) blatantly lied, promising them amusements far superior tho those which so enchanted them. The leader of a caravan, knowing that they were almost there if they could only summon the strength to push on a little longer, just as everyone was so exhausted and discouraged they were on the verge of giving up and going home, created a mirage of a golden city; by deception enticing them to drive on. The physician upon arriving home found that his children had gotten into his stores and poisoned themselves. Unable to coax them into taking the antidote, he left, then send word that he had died, and his dying wish was that his children would comply and take the medicine he had prescribed for them.
The saha world is a complicated, confusing, and messy place, where rigid legalism and simplistic notions of good and evil frequently have unintended and untoward consequences, sometimes exacerbating rather than ameliorating a situation. A bodhisattva not only acts ethically, but to applies those ethics skillfully, for the benefit of all beings. That requires some wisdom, creativity, and flexibility which rigid legalism precludes. However imperfectly, we do the best we can.