Maybe you could get someone to conduct you and your accompanist? That might help a little bit but make sure they know the score.
They will follow you, but you don't want to make it too difficult for them, so your changes of tempo should be predictable and consistent, your rubato more restrained than when playing solo.It can help to practice with a metronome, even though you won't perform that robotically. It's a duet, each side must listen and adjust to the other.
Congratulations!!!Here is some advice:-between now and February make sure you know the concerto back and forth, including the orchestra part-practice with metronome-in February contact the conductor and see about getting together with him a few days before the first rehearsal to work out any kinks-remember that it is a dialogue between orchestra and soloist, however as the soloist, you need to take charge and lead.-from what I am reading, it seems you will be playing the Schumann. Be very careful with the 3rd movement. The 3rd movement has a few passages that are tricky.