I think that the current cup mechanism is to arrange matches between two teams having similar quality. That's why, despite that your opponent is 3 levels above you, your team's rating is about equal to his team's.

On the other hand, I think that 4-3n-3 formation will attack in the middle and will be very effective with counterattack, because your opponent just need a long pass to feed the ball to his 3 ST already being wandered in your penalty box. Therefore, it is crucial to put a DMC to help the DC against those long passes, and I think your red arrow on DMC is not a good choice. Please check the rating of your DMC and 2DC if I was wrong.