Hello there, overachiever!
It is entirely ok to not score perfectly on SC as long as your Verbal score overall demonstrates mastery. With that said, if you're aiming to get all SC questions right, I think you already know that not knowing the rules is not the issue. If you share with us what kind of mistakes you made, we may be able to give you some advice on your particular situation.
Now here's the general way to achieve perfection. If you make a mistake, take it to heart. Generalize the kind of mistake you made, and do not allow yourself to make the same mistake again. Ever. Punish yourself very hard if you repeat a mistake of the past. This requires a lot of focus and discipline, and this is exactly what I impose on my students.
Now I don't think you need a tutor. If you want a perfect SC performance bad, I think you can impose the discipline on yourself. If not, just move on with your life and shift your energy to making sure that you hit that 96th percentile consistently - ultimately this is what matters for business school applications.
Good luck!