“How do you plan to protect (answer to second question here)?”
If the role of a Jedi, as Mace Windu put it in Matthew Stover’s Shatterpoint, is to protect civilization, then it should come as no surprise that our organization sees the Prowess section as being key to aiding in that mission. Each art we develop is intended to help further that goal. Depending on the adventure you have been called to, at least one of the Arts should take precedence.
That’s to say, if your adventure is to become a doctor, then the Scholarly Art will take precedence in your prowess development. That doesn’t mean you ignore the other three arts. The Spiritual Art helps you maintain your center, your Physical Art will aide you in the stamina and focus you need to do your job as a doctor, and your defense art (be it in communication, or even learning to physically restrain a violent patient) will give you the edge needed to maintain order when things get out of hand.
The third question is answered by understanding, growing and committing to your prowesses. A doctor might say “I will continue to stay on top of the latest information in my field, so that my patients receive the best practices”.
A teacher who has placed their Spiritual Art at the head of their adventure and wants to protect students from child abuse, may say “I will continue to work on being a warm and welcoming teacher so that my students feel safe coming to me about their problems.”
A Master’s answer to this question shouldn’t be something they simply plan to do, but rather a synthesis of what they already have started doing as a Knight, and how they plan to advance it as they continue to carry out the will of the Force in their life.