Do not rule out neuromuscular imbalance and musculoskeletal misalignment. Depending on the extent and scope of any imbalances or misalignment, migraine and balance issues may be related. Is one leg shorter than the other? Do you have a anterior, posterior, and/or lateral pelvic tilt? Do you have uneven shoulders? Does the middle of your neck go one way and your atlas go another? Is your jaw misaligned? Do you have forward head posture?
All worth investigating. Your body can misalign bottom-up and/or top-down and this can come with a whole series of cascading issues.