BFA you bes "spot on" about the schoolmaster. Clearly points to the MORAL law and indicates all reference to it ceases when we come to Christ. We no longer measure right and wrong by written codes and shibboleths and man-made constructs but by the heart of Jesus Christ manifest first in His life and death for us and His teaching and next through our direct firsthand experience in and with the Holy Spirit.
As for the "bondwoman" -- well, Hagar represents Abraham's botched works resulting from the belief that he had to PROVE his faith by DOING SOMETHING to make the promise happen. Many shipwreck themselves on precisely this point today when it comes to faith and "works", failing totally to comprehend that scripture makes it clear any and all righteous doings through us originate with God and come from His hand, not our own manufacturing by rules, rulemaking, or human efforts (including the so-called "right action of the will").
Getting rid of the bondwoman means getting rid of the delusion that we must prove the sincerity of our faith by accomplishing what it promises WILL be the ultimate fulfillment of the Mystery of God: Christ fully formed IN us, the hope of glory. It bes by grace ALONE through faith ALONE and the only "works" that make faith not "dead" being the works that GOD created and ordained to occur THROUGH us, NOT anything we can do ourselves. the New Testament bes replete with such language pointing out that our efforts can only result in sin and the only way to NOT walk in the flesh or fulfill the sin nature bes to walk in the Spirit -- NOT to focus on "trying not to sin".
Be blessed, resting in Him whose yoke bes EASY and burden LIGHT.